If 15 boys earn ₹900 in 5 days, then how much will 20 boys earn in 7 days?
Explanation:
15 boys earn ₹900 in 5 days
∴ Earning per boy per day = 900/(5 × 15) = Rs. 12
∴ Earnings of 20 boys in 7 days = 12 × 20 × 7 = Rs. 1680
Hence, option (b).