Question : Directions: By interchanging the two signs ÷ and + and two numbers 9 and 12 (NOT digits), which of the following equations will NOT be correct?
I. 12 × 2 – 72 + 9 ÷ 57 = 69
II. 169 + 13 × 12 ÷ 3 – 9 = 108
Option 1: Neither I nor II
Option 2: Both I and II
Option 3: Only II
Option 4: Only I
Correct Answer: Neither I nor II
Solution :
Given:
I. 12 × 2 – 72 + 9 ÷ 57 = 69
II. 169 + 13 × 12 ÷ 3 – 9 = 108
Equation I:
12 × 2 – 72 + 9 ÷ 57 = 69
On interchanging the mathematical signs and numbers, we get –
9 × 2 – 72 ÷ 12 + 57 = 69
On solving the L.H.S. of the equation –
= 9 × 2 – 72 ÷ 12 + 57
= 9 × 2 – 6 + 57
= 18 – 6 + 57
= 69
Equation II:
169 + 13 × 12 ÷ 3 – 9 = 108
On interchanging the mathematical signs and numbers, we get –
169 ÷ 13 × 9 + 3 – 12 = 108
On solving the L.H.S. of the equation –
= 169 ÷ 13 × 9 + 3 – 12
= 13 × 9 + 3 – 12
= 117 + 3 – 12
= 108
So, neither equation I nor II is incorrect. Hence, the first option is correct.
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