Algebra for Class 6 - Expression, Operations and Rules

Algebra For Class 6

Edited By Team Careers360 | Updated on Jul 02, 2025 05:27 PM IST

If we wish to define what is algebra, we can say it as a branch of mathematics in which we use letters to denote numbers. Now these letters are nothing but the english alphabets that we have studied and known so far. In algebra, we assume the value of some unknown numerical constant to be a variable in an equation and then we solve the equation till we find the unknown quantity.

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What is Algebra?
Algebra Class 6 Notes
Algebra Class 6 Questions and Answers

Algebra For Class 6

This article is about the concept of algebra class 6 ncert. In this article, we will learn about introduction to algebra class 6, the basics of algebra, algebra class 6 solutions, etc.

What is Algebra?

Algebra is a branch of mathematics that deals with variables and constants. An algebraic expression is a combination of variables and constant. Algebra includes almost everything ranging from solving elementary equations to the study of abstractions. It is really helpful in finding the unknown quantities assuming them as variables and solving the equations.

We use letters called variables, to represent the unknown quantities in maths. The use of letters helps us in various ways as listed below:

It makes the process of writing rules and formulas in very simple way.
We do not have to talk about just one number but we can talk of many numbers at the same time.
The variables help us to represent unknown quantities and solve daily life problems within no time.
They also enable us to perform mathematical operations like addition, subtraction, multiplication, and division on numbers in form of variables.

Algebra Class 6 Notes

Algebra class 6 notes include the concepts of variables and constants, algebraic equations and how to solve such equations.

Variable and Constants

A variable is a quantity that may change. Hence, its value is not fixed and may take different values. Variables are expressed as small letters like a,b,c,x,y,z,....

A constant is a quantity that does not change.

For example, you and your friend go to buy pencils. The cost of one pencil is Rs. 5. The amount to be paid is $5x$ where $x$ is the number of pencils. You buy 5 pencils and your friend buys 4 pencils. Here, the value of $x$ is 5 and 4. From this, we could say that the value of $x$ is not fixed, it keeps on changing. So, $x$ is a variable.

But the price of the pencil is not going to change. So, the cost of one pencil that is Rs.5 is a constant.

Similarly, consider the area of square formula, $A = x^2$. Here, the length of the side$(x)$ is not fixed. So, $x$ is a variable. But the number sides in a square is always four. So, 4 is a constant.

Algebraic Equations

Algebraic equations are combinations of variables and constant. Eg. $2x=38$, $3x+7y=22$, etc.

Algebraic equations with one variable

Let us consider the previous example. You go to buy pencils. The cost of one pencil is Rs. 5. You pay Rs.35 to the shopkeeper. Let $x$ be the number of pencils.

Now, let us form a algebraic equation for this situation. The algebraic equation is $5x = 35$ where $x$ is the number of pencils.

By solving this equation, we can find the number of pencils you bought.

Now, let us look into another example to understand the algebraic equation with two variables.

Algebraic equations with two variables

Raju and Balu are brothers. When Raju is 12 years old, Balu is 9 years old. When Raju is 15 years old, Balu is 12 years old. From this, we could say that Raju is 3 years older than Balu.

Now let $y$ be Raju's age and $x$ be Balu's age. This can be expressed as a algebraic equation as $y = x+3$. If we know Balu's age, then, we can put the value in $x$ and find Raju's age. Suppose Balu is 20 years old, then Raju's age is, $y=20+3 = 23$.

Similarly, if we know Raju's age, then, we can put the value in $y$ and find Balu's age. Suppose Raju is 17 years old, then Balu's age is, $17 = x+3$. This can be written as $x=17-3 = 14$. So, Balu is 14 years old when Raju is 17 years old.

How do we solve an algebraic equation?

We solve equations until the left hand side equation is equal to right hand side equaiton. For example, equation 2x = 4 is satisfied for the value of x = 2 only. As we can write $x = \frac{4}{2} = 2$.

Now, let us look into some algebra class 6 extra questions.

Algebra Class 6 Questions and Answers

Example 1: Cadets are marching in a Republic Day parade. There are 10 cadets in a row. Find out the rule which gives the number of cadets.

Solution: Let us suppose that $p$ be the number of rows
Given that number of cadets present in a row $=10$
Hence total number of cadets $=$ number of cadets in a row $\times$ total number of rows $
=10 p
$

Example 2: If there are $\mathbf{2 0}$ pencils in a box, how will you write the total number of pencils in terms of the number of boxes?

Solution: Let us suppose that $x$ be the number of boxes
Given that number of pencils in a box $=20$
Hence total number of pencils $=$ number of pencils in a box $\times$ total number of boxes $=20 x$

Example 3: The professor in a college distributes 2 fountain pens per student. Can you tell how many pens are needed in all ?

Solution: Let us take $r$ be the total number of students
From question, pens given to each student $=2$
Therefore total number of pens $=$ number of pens given to each student $\times$ total number of students $=2 \mathrm{r}$

Example 4: An eagle flies 3 km in one minute. Express the distance covered by the eagle in terms of its flying time in minutes.

Solution: Let z minutes be the flying time
We are given that distance covered in one minute $=3 \mathrm{~km}$
Hence, distance covered in z minutes $=$ Distance covered in one minute $\times$ total flying time $=1 \times z=z \mathrm{~km}$

Example 5: The side of a square is denoted by p. Express the perimeter of the square using
p.

Solution: Side of square $=p$
Perimeter of square $=p+p+p+p=4 p$

List of Topics Related to Algebra Class 6

Algebra	Algebraic Identities Class 8
Algebraic Expressions	Algebraic Identities Class 9
a cube plus b cube

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Frequently Asked Questions (FAQs)

1. What is the purpose of algebra ?

It helps us to determine unknown quantities in various situations.

2. What are types of algebra ?

It includes linear algebra, commutative algebra, abstract algebra, etc.

3. What are 4 basic rules of algebra ?

They are commutative rule of addition, multiplication, associative rule and distributive rule.

4. What is algebra class 6?

Algebra is a branch of mathematics that deals with variables and constants. An algebraic expression is a combination of variables and constant. It is really helpful in finding the unknown quantities assuming them as variables and solving the equations.

5. What is a variable ?

It can assume any value and represents unknown quantities.

6. How do you add two integers with different signs?

To add integers with different signs, subtract the smaller absolute value from the larger one and keep the sign of the number with the larger absolute value. For example, 5 + (-3) = 2, because |5| > |-3|, so we do 5 - 3 = 2.

7. Why does multiplying two negative numbers result in a positive number?

Multiplying two negative numbers gives a positive result because it's like applying a negative operation (reversing direction) twice. Think of it as "undoing a negative," which results in a positive. This concept is consistent with the patterns we observe in integer multiplication.

8. How do exponents work, and why are they useful in representing large or small numbers?

Exponents are a shorthand way of expressing repeated multiplication. They're useful for representing very large or very small numbers concisely (e.g., 10^6 for 1,000,000). Exponents simplify calculations and help express numbers in scientific notation.

9. What is the difference between squaring a number and finding its square root?

Squaring a number means multiplying it by itself (e.g., 3^2 = 3 × 3 = 9). Finding the square root is the inverse operation, determining what number, when multiplied by itself, gives the original number (e.g., √9 = 3). Understanding this relationship helps in solving equations and real-world problems.

10. How can you represent decimal numbers as fractions?

To convert a decimal to a fraction, write the decimal as a fraction over powers of 10 (e.g., 0.25 = 25/100), then simplify if possible. For repeating decimals, use algebraic methods to find the equivalent fraction. This conversion helps in understanding the relationship between decimals and fractions.

11. What is the additive inverse of an integer, and why is it important?

The additive inverse of an integer is the number that, when added to the original integer, gives a sum of zero. For example, the additive inverse of 5 is -5. It's important because it helps us understand subtraction as adding the additive inverse.

12. How does multiplication of integers work with different signs?

When multiplying integers, the product is positive if both factors have the same sign (positive × positive or negative × negative). The product is negative if the factors have different signs (positive × negative or negative × positive).

13. Why isn't zero considered a natural number?

Zero isn't considered a natural number because natural numbers are used for counting objects, and you can't count zero objects. Natural numbers represent quantities that exist, while zero represents the absence of quantity.

14. What are integers, and how do they differ from whole numbers?

Integers include all whole numbers and their negative counterparts (..., -3, -2, -1, 0, 1, 2, 3, ...). They differ from whole numbers by including negative numbers, allowing us to represent quantities below zero.

15. How do you express a fraction in its lowest terms?

To express a fraction in its lowest terms, divide both the numerator and denominator by their HCF. This process, called simplification, helps in comparing fractions and performing operations with them more easily.

16. Can you give an example of a number that is not rational?

Yes, numbers that cannot be expressed as fractions of integers are called irrational numbers. A famous example is π (pi), which has an infinite, non-repeating decimal representation.

17. What is the absolute value of a number, and how does it relate to integers?

The absolute value of a number is its distance from zero on a number line, regardless of whether it's positive or negative. For integers, the absolute value tells us how far a number is from zero, ignoring its sign.

18. How do you compare two negative integers?

When comparing negative integers, the number closer to zero is greater. For example, -3 is greater than -5 because -3 is closer to zero on the number line. Think of it as being "less negative."

19. What are natural numbers, and how are they different from whole numbers?

Natural numbers are the counting numbers starting from 1 (1, 2, 3, 4, ...). Whole numbers include all natural numbers plus zero (0, 1, 2, 3, ...). The main difference is that whole numbers include zero, while natural numbers don't.

20. What are rational numbers, and how do they relate to integers?

Rational numbers are numbers that can be expressed as a fraction of two integers (where the denominator is not zero). All integers are rational numbers because they can be written as a fraction with 1 as the denominator (e.g., 5 = 5/1).

21. How do you solve equations with variables on both sides?

To solve equations with variables on both sides, use algebraic methods to isolate the variable on one side. This often involves using inverse operations and the principle of equality (performing the same operation on both sides). Understanding this process is fundamental to more advanced algebra.

22. What is the concept of variables, and how do they differ from constants?

Variables are symbols (usually letters) that represent unknown or changing values. Constants are fixed values that don't change in a given context. Understanding the difference helps in creating and interpreting algebraic expressions and equations.

23. How do you represent real-world situations using algebraic expressions?

To represent real-world situations algebraically, identify the unknown quantity and use a variable to represent it. Then, translate the given information into mathematical operations. This skill is essential for problem-solving and modeling real-world scenarios.

24. What is the difference between an expression and an equation?

An expression is a combination of numbers, variables, and operations without an equal sign (e.g., 2x + 3). An equation is a statement that two expressions are equal (e.g., 2x + 3 = 11). Recognizing this difference is crucial for proper problem-solving and algebraic manipulation.

25. What is the order of operations, and why is it important?

The order of operations (PEMDAS: Parentheses, Exponents, Multiplication and Division from left to right, Addition and Subtraction from left to right) ensures consistent evaluation of mathematical expressions. It's crucial for avoiding ambiguity and getting correct results in complex calculations.

26. How can you visualize positive and negative integers on a number line?

On a number line, positive integers are placed to the right of zero, negative integers to the left. Each integer is equally spaced, with zero in the center. This visual representation helps understand the relationship between positive and negative numbers.

27. What is the concept of divisibility, and how does it relate to factors?

Divisibility is the property of a number being evenly divided by another number without a remainder. A factor is a number that divides another number evenly. Understanding divisibility helps in identifying factors and understanding number relationships.

28. What is the difference between factors and multiples?

Factors are numbers that divide evenly into another number, while multiples are the products of a number and an integer. For example, factors of 12 are 1, 2, 3, 4, 6, and 12. Multiples of 3 are 3, 6, 9, 12, 15, and so on.

29. How do you find the HCF (Highest Common Factor) of two or more numbers?

To find the HCF, list all factors of each number and identify the largest factor common to all numbers. Alternatively, you can use the prime factorization method or the division method (for two numbers). Understanding HCF helps in simplifying fractions and solving real-world problems.

30. What is the relationship between HCF and LCM (Least Common Multiple)?

The product of the HCF and LCM of two numbers is equal to the product of those two numbers. This relationship helps in finding one when the other is known: HCF × LCM = Number 1 × Number 2.

31. How do prime numbers relate to factors and divisibility?

Prime numbers have exactly two factors: 1 and themselves. They play a crucial role in factorization because every number can be expressed as a product of prime factors. This concept is fundamental in understanding divisibility and factor relationships.

32. Why is 1 not considered a prime number?

1 is not considered prime because prime numbers are defined as having exactly two factors. 1 only has one factor (itself), making it neither prime nor composite. This definition helps maintain certain properties of prime numbers in number theory.

33. How can you use prime factorization to find the HCF and LCM?

To find HCF: Prime factorize the numbers and multiply the common prime factors using the lowest exponents.

34. What are co-prime numbers, and why are they important?

Co-prime numbers (or relatively prime numbers) are numbers whose HCF is 1. They don't share any common factors other than 1. Co-prime numbers are important in various mathematical concepts, including fractions and modular arithmetic.

35. What is the difference between proper and improper fractions?

A proper fraction has a numerator smaller than its denominator (e.g., 3/4), while an improper fraction has a numerator greater than or equal to its denominator (e.g., 5/4). Improper fractions can be expressed as mixed numbers.

36. How do you convert an improper fraction to a mixed number?

To convert an improper fraction to a mixed number, divide the numerator by the denominator. The quotient becomes the whole number part, and the remainder becomes the numerator of the fractional part, keeping the same denominator.

37. What is the reciprocal of a fraction, and how is it used in division?

The reciprocal of a fraction is found by flipping the numerator and denominator. When dividing fractions, we multiply by the reciprocal of the divisor. This method simplifies fraction division to multiplication, making the process easier.

38. How do you round numbers, and why is it useful?

Rounding involves approximating a number to a certain place value. It's useful for estimating, simplifying calculations, and presenting data in a more manageable form. The general rule is to round up if the digit to the right is 5 or greater, and round down if it's less than 5.

39. What is the concept of significant figures, and how does it relate to precision?

Significant figures are the digits in a number that carry meaning contributing to its precision. They include all certain digits and the first uncertain digit. Understanding significant figures helps in reporting measurements and calculations with appropriate precision.

40. How do you estimate square roots without a calculator?

To estimate square roots, find the two perfect squares the number falls between and estimate its position. For example, √20 is between √16 (4) and √25 (5), closer to 4.5. This skill is useful for mental math and approximations.

41. How can you determine if a number is divisible by 2, 3, or 5 without actually dividing?

For 2: If the last digit is even (0, 2, 4, 6, or 8).

42. Why is it important to find a common denominator when adding or subtracting fractions?

A common denominator is necessary when adding or subtracting fractions because we can only combine like terms. By finding a common denominator, we create equivalent fractions that can be easily added or subtracted.

43. How do you multiply fractions, and why does the process seem simpler than addition?

To multiply fractions, multiply the numerators together and the denominators together. This process is simpler than addition because you don't need to find a common denominator. The simplicity comes from the distributive property of multiplication over addition.

44. What is the difference between terminating and repeating decimals?

Terminating decimals have a finite number of digits after the decimal point (e.g., 0.25). Repeating decimals have a digit or group of digits that repeat indefinitely (e.g., 0.333...). All terminating and repeating decimals are rational numbers.

45. How do you simplify algebraic expressions by combining like terms?

Combining like terms involves adding or subtracting terms with the same variables raised to the same powers. For example, 3x + 2y + 5x - y simplifies to 8x + y. This process is fundamental in algebraic manipulation and equation solving.

46. What is the distributive property, and how is it used in algebra?

The distributive property states that a(b + c) = ab + ac. It's used to multiply a number or variable by a sum or difference. This property is crucial for expanding expressions, factoring, and solving equations.

47. How do you factor algebraic expressions, and why is it useful?

Factoring involves finding the factors of an algebraic expression. Common techniques include finding common factors, grouping, and recognizing special patterns. Factoring is useful for simplifying expressions, solving equations, and understanding the structure of polynomials.

48. What are linear equations, and how do they relate to straight lines?

Linear equations are equations where the variable has a degree of 1 (e.g., y = mx + b). They represent straight lines when graphed on a coordinate plane. Understanding linear equations is fundamental to graphing and solving many real-world problems.

49. How do you interpret the slope and y-intercept of a linear equation?

In the equation y = mx + b, m represents the slope (rate of change) and b represents the y-intercept (where the line crosses the y-axis). Interpreting these values helps in understanding the behavior and position of the line.

50. What is the difference between discrete and continuous data?

Discrete data can only take specific values (like whole numbers), while continuous data can take any value within a range. Understanding this difference is important for choosing appropriate mathematical models and representations.

51. How do you represent and interpret inequalities on a number line?

Inequalities are represented on a number line using open or closed circles for the endpoint and a line or arrow to show the included values. This visual representation helps in understanding the range of values that satisfy the inequality.

52. What is the concept of absolute value, and how does it relate to distance?

The absolute value of a number is its distance from zero on a number line, regardless of direction. It's always non-negative and relates to the concept of magnitude or distance. Understanding absolute value is crucial for solving certain types of equations and inequalities.

53. How do you solve word problems involving rates, time, and distance?

To solve rate-time-distance problems, use the formula Distance = Rate × Time. Identify the given information and the unknown, then set up an equation to solve. This approach helps in tackling many real-world problems involving motion and speed.

54. What is the difference between ratio and proportion?

A ratio is a comparison of two quantities, while a proportion is an equation stating that two ratios are equal. Understanding the relationship between ratios and proportions is crucial for solving problems involving scaling, mixtures, and comparisons.

55. How do you use cross multiplication to solve proportions?

Cross multiplication is a method for solving proportions by multiplying the numerator of each fraction by the denominator of the other fraction. This technique simplifies the process of solving proportions and is widely used in various applications.