Question

Which two signs should be interchanged to make the given equation correct?

341 ÷ 11 - 15 × 8 + 100 = 51

1. × and -
2. - and +
3. × and +
4. + and ÷ 

Answer 1

Correct Answer - Option 2 : - and +

The given equation:
341 ÷ 11 - 15 × 8 + 100 = 51
On interchanging × and -,

we get:
341 ÷ 11 × 15 - 8 + 100 = 51
⇒ 31 × 15 + 92 = 51

⇒ 557 = 51 (false)

On interchanging - and +, 

we get:
341 ÷ 11 + 15 × 8 - 100
⇒ 31 + 120 - 100 = 51
⇒ 31 + 20 = 51 (true)

On interchanging × and +,

we get:
341 ÷ 11 - 15 + 8 × 100 = 51
⇒ 31 - 15 + 800 = 51

⇒ 816 = 51 (false)
On interchanging + and ÷,

we get:
341 + 11 - 15 × 8 ÷ 100 = 51
⇒ 352 - 1.2 = 51 
⇒ 350.8 = 51(false)

Hence, we need to interchange + and - to make the equation correct.