Question : Directions: Which two signs and two numbers (Not digits) of the equation should be interchanged to make it correct?
13 × 12 ÷ 36 + 11 – 7 = 35

Option 1: + and ×, 36 and 7

Option 2: + and –, 12 and 7

Option 3: × and ÷, 13 and 36

Option 4: × and ÷,11 and 7

Correct Answer: × and ÷,11 and 7

Solution : Given:
13 × 12 ÷ 36 + 11 – 7 = 35

Let's check the given options –
First option: + and ×, 36 and 7
13 × 12 ÷ 36 + 11 – 7 = 35
On interchanging the mathematical signs and numbers, we get –
= 13 + 12 ÷ 7 × 11 – 36
= 13 + 1.71 × 11 – 36
= 13 + 18.81 – 36
= 31.81 – 36
= –4.19 ≠ 35
Second option: + and –, 12 and 7
13 × 12 ÷ 36 + 11 – 7 = 35
On interchanging the mathematical signs and numbers, we get –
= 13 × 7 ÷ 36 – 11 + 12
= 13 × 0.19 – 11 + 12
= 2.47 – 11 + 12
= 3.47 ≠ 35
Third option: × and ÷, 13 and 36
13 × 12 ÷ 36 + 11 – 7 = 35
On interchanging the mathematical signs and numbers, we get –
= 36 ÷ 12 × 13 + 11 – 7
= 3 × 13 + 11 – 7
= 39 + 11 – 7
= 50 – 7
= 43 ≠ 35
Fourth option: × and ÷,11 and 7
13 × 12 ÷ 36 + 11 – 7 = 35
On interchanging the mathematical signs and numbers, we get –
= 13 ÷ 12 × 36 + 7 – 11
= 39 + 7 – 11
= 46 – 11
= 35

So, the fourth option satisfies the R.H.S. of the equation. Hence, the fourth option is correct.