(Suitable for Primary 4)
Bag A and Bag B had an equal amount of rice at first. After 22.4 kg and 16.8 kg of rice were removed from Bag A and Bag B, respectively, Bag B had thrice as much rice as Bag A. How much rice did each bag have at first?
When do we draw 1 model when it is a “Before Change After” concept?
We record in 1 model when the value of the change is known or given.
However, if the value of the change is NOT known, we propose to record it in “Before Change After” format.
3 units – 1 unit = 2 units
2 units = 22.4 kg – 16.8 kg
= 5.6 kg
1 unit = 5.6 kg ÷ 2
= 2.8 kg
2.8 kg + 22.4 kg = 25.2 kg
Answer: 25.2 kg