A man notices that a tank is half full. After emptying 600 litres from the tank, that it is now one-third full. How much does the tank hold when it is full?

One half is equal to 3/6.

One third is equal to 2/6.

After removing 600 litres from the tank, there is a decrease from 3/6 to 2/6

3/6-2/6=1/6

600 litres is 1/6 of the tank. Multiply by 6 to get the capacity of a full tank.

600*6=3600

The tank can hold 3600 litres.