Put on 2 meters long and change it to: 2 decimeters.

20 hours becomes: 20 seconds.

Pick up a glass of 250 kilograms of milk and change it into 250 grams.

Carrying a 2.5-ton schoolbag has become: 2.5 kilograms.

Ask again if you don't understand. I wish you progress in your study and go up a storey still higher! (*^__^*)