Correct Answer - Option 2 : 18

**Given:**

By selling 45 mangos for Rs. 40 the seller losses 20%. He needs to gain 20% on selling mangoes for Rs. 24.

**Concept Used:**

Expenditure (E) = Price (P) × Quantity (Q)

**Calculation:**

In Rs. 40 he sold 45 mangoes

In Rs. 24 he sold (45/40) × 24 = 27 mangoes

In 1^{st} case he losses 20%

Selling price is (P_{1}) = (100 – 20) = 80%

In 2^{nd} case, he gains 20%

Selling price is (P_{2}) = (100 + 20) = 120%

In 1^{st} case number of mangoes (Q_{1}) = 27

We have to find the number of mangoes in 2^{nd} case Q_{2}

Here in both case expenditure is same.

P_{1} × Q_{1} = P_{2} × Q_{2}

⇒ 80 × 27 = 120 × Q_{2}

⇒ Q_{2} = (80 × 27)/120

⇒ Q_{2} = 18

**∴**** He has to sell 18 mangoes for Rs. 24 to gain 20%.**