Question : Directions: Which two signs should be interchanged to make the given equation correct?
81 + 3 ÷ 9 * 5 − 12 = 60
Option 1: ÷ and +
Option 2: + and ×
Option 3: ÷ and −
Option 4: + and −
Correct Answer: ÷ and +
Solution :
Given:
81 + 3 ÷ 9 * 5 − 12 = 60
Replace the given signs in the options one by one with the original signs in the given equation.
First option:
÷ and +
= 81 ÷ 3 + 9 × 5 – 12
= 27 + 9 × 5 – 12
= 27 + 45 – 12
= 60
Second option:
+ and ×
= 81 × 3 ÷ 9 + 5 − 12
= 27 + 15 − 12
= 30 ≠ 60
Third option:
÷ and −
= 81 + 3 – 9 × 5 ÷ 12 = 60
= 81 + 3 – 9 × 0.416
= 81 + 3 – 3.75
= 80.25 ≠ 60
Fourth option:
+ and −
= 81 – 3 ÷ 9 × 5 + 12
= 81 – 0.33 × 5 + 12
= 81 – 1.66 + 12
= 91.33 = R.H.S.
So, only the first option satisfies the R.H.S. of the given equation. Hence, the
first option
is correct.
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