Question : Directions: Which two numbers should be interchanged to make the given equation correct?
81 + 31 ÷ 9 – 7 = 33
Option 1: 9 and 7
Option 2: 31 and 9
Option 3: 31 and 81
Option 4: 81 and 7
Correct Answer: 31 and 81
Solution :
Given:
81 + 31 ÷ 9 – 7 = 33
Let's check the options –
First options:
9 and 7
81 + 31 ÷ 7 – 9 = 33
On solving the L.H.S. of the given equation –
= 81 + 31 ÷ 7 – 9
= 81 + 4.43 – 9
= 76.43 ≠ 33
Second option:
31 and 9
81 + 9 ÷ 31 – 7 = 33
On solving the L.H.S. of the given equation –
= 81 + 9 ÷ 31 – 7
= 81 + 0.29 – 7
= 74.29 ≠ 33
Third option:
31 and 81
31 + 81 ÷ 9 – 7 = 33
On solving the L.H.S. of the given equation –
= 31 + 81 ÷ 9 – 7
= 31 + 9 – 7
= 33
Fourth option:
81 and 7
7 + 31 ÷ 9 – 81 = 33
On solving the L.H.S. of the given equation –
= 7 + 31 ÷ 9 – 81
= 7 + 3.44 – 81
= –70.56 ≠ 33
So, the third option satisfies the equation. Hence, the third option is correct.
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