Which two numbers have to be interchanged to correct the given equation? 

55 + 32 - 4 × (1 × 12) + (16 ÷ 4) = 31 

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  1. 16 and 32
  2. 55 and 32
  3. 12 and 32
  4. 12 and 16

Answer (Detailed Solution Below)

Option 1 : 16 and 32
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Detailed Solution

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1) 16 and 32

Given equation: 55 + 32 – 4 × (1 × 12) + (16 ÷ 4) = 31

After interchanging ‘16 and 32’, we get:

L.H.S = 55 + 16 – 4 × (1 × 12) + (32 ÷ 4)

= 55 + 16 – 4 × 12 + 8

= 55 + 16 – 48 + 8

= 79 – 48

= 31 = R.H.S

2) 55 and 32

Given equation: 55 + 32 – 4 × (1 × 12) + (16 ÷ 4) = 31

After interchanging ‘55 and 32’, we get:

L.H.S = 32 + 55 – 4 × (1 × 12) + (16 ÷ 4)

= 32 + 55 – 4 × 12 + 4

= 32 + 55 – 48 + 4

= 32 + 23 + 3

= 58 ≠ R.H.S

3) 12 and 32

Given equation: 55 + 32 – 4 × (1 × 12) + (16 ÷ 4) = 31

After interchanging ‘12 and 32’, we get:

L.H.S = 55 + 12 – 4 × (1 × 32) + (16 ÷ 4)

= 55 + 12 – 4 × 32 + 4

= 55 + 12 – 128 + 4

= 71 – 128

= - 57 ≠ R.H.S

4) 12 and 16

Given equation: 55 + 32 – 4 × (1 × 12) + (16 ÷ 4) = 31

After interchanging ‘12 and 16’, we get:

L.H.S = 55 + 32 – 4 × (1 × 16) + (12 ÷ 4)

= 55 + 32 – 4 × 16 + 3

= 55 + 32 – 64 + 3

= 90 – 64

= 26 ≠ R.H.S

Hence, ‘16 and 32’ is the correct answer
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