Answer: 3,240,000 L
Step-by-step explanation:
Each tree requires 20 L of water per day for 180 days.
Each tree therefore requires;
= 20 * 180
= 3,600 L per day
There are 900 trees to be grown;
= 900 * 3,600
= 3,240,000 L of water are required for 900 trees.