Correct Answer - Option 3 : 300

**Given:**

Denominations of coins = 50 paisa, 25 paisa and 10 paisa

Ratio = 5 ∶ 7 ∶ 9

Total amount = Rs. 309

**Calculation:**

Let the number of 50 paisa, 25 paisa and 10 paisa coins be 5x, 7x and 9x respectively.

According to question

(5x/2) + (7x/4) + (9x/10) = 309

⇒ (50x + 35x + 18x)/20 = 309

⇒ 103x = 309 × 20

⇒ x = (309 × 20)/103

⇒ x = 3 × 20

⇒ x = 60

Number of 50 paisa coins = 5x

⇒ 5 × 60

⇒ 300

**∴ The number of 50 paisa coins are 300.**