Question : Directions: Which two signs should be interchanged to make the given equation correct?
117 ÷ 13 + 16 × 540 – 40 = 644
Option 1: ÷ and +
Option 2: + and ×
Option 3: – and +
Option 4: ÷ and –
Correct Answer: + and ×
Solution :
Given:
117 ÷ 13 + 16 × 540 – 40 = 644
Replace the given symbols in the options one by one with the original symbols in the given equation –
First option:
÷ and +
= 117 + 13 ÷ 16 × 540 – 40
= 117 + 0.812 × 540 – 40
= 117 + 438.48 – 40
= 555.48 – 40
= 515.48 ≠ 644
Second option:
+ and ×
= 117 ÷ 13 × 16 + 540 – 40
= 9 × 16 + 540 – 40
= 144 + 540 – 40
= 684 – 40
= 644
Third option:
– and +
= 117 ÷ 13 – 16 × 540 + 40
= 9 – 16 × 540 + 40
= 9 – 8640 + 40
= 49 – 8640
= –8591 ≠ 644
Fourth option:
÷ and –
= 117 – 13 + 16 × 540 ÷ 40
= 117 – 13 + 16 × 13.5
= 117 – 13 + 216
= 333 – 13
= 320 ≠ 644
So, only the second option satisfies the R.H.S. of the given equation. Hence, the second option is correct.
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