A village has 5 stagnant pools each holding 200 litres of water. A mosquito species lays eggs at a rate of 1 egg per litre per day. If every egg hatches into a larva that consumes 2 ml of water before pupation, how much water remains after all larvae have consumed it in 7 days?

Step-by-step solution

1. Compute daily eggs per pool: 200 litres × 1 egg/litre = 200 eggs.
2. Total daily eggs for 5 pools: 200 × 5 = 1000 eggs.
3. Eggs laid in 7 days: 1000 × 7 = 7000 eggs.
4. Each larva consumes 2 ml = 0.002 litre.
5. Total water consumed: 7000 × 0.002 = 14 litres.
6. Initial water in all pools: 5 × 200 = 1000 litres.
7. Remaining water: 1000 – 14 = 986 litres.

Concept tested: Water consumption by mosquito larvae

Published 7 October 2026 · How this solution was prepared and checked