Correct Answer: ÷ and ×

Solution : Given:
3 ÷ 1 + 6 × 2 – 5

Interchange the signs according to the given options.
First option: + and –
Solving the L.H.S. of the equation –
3 ÷ 1 – 6 × 2 + 5
= 3 – 12 + 5
= –4 ≠ 1
Second option: ÷ and +
Solving the L.H.S. of the equation –
3 + 1 ÷ 6 × 2 – 5
= 3 + 0.334 – 5
= –1.666 ≠ 1
Third option: x and –
Solving the L.H.S. of the equation –
3 ÷ 1 + 6 – 2 x 5
= 3 + 6 – 10
= –1 ≠ 1
Fourth option: ÷ and x
Solving the L.H.S. of the equation –
= 3 x 1 + 6 ÷ 2 – 5
= 3 x 1 + 3 – 5
= 6 – 5
⇒ 1 = 1

So, after interchanging ÷ and x, the equation equals 1. Hence, the fourth option is correct.