M4.2.1 For the adult
Percentage increase and decrease
How do I add 12% to 250 in one step?
What this chapter teaches
A percentage rise or fall is one multiplication. A rise of 12% is a multiplier of 1.12 and a fall of 35% is 0.65. A percentage change always compares the change with the amount you started from.
Three questions to ask
There is no one right wording. Listen for the idea.
- What number do you multiply by to take 20% off?
- Why do we divide by the original amount when we find a percentage change?
- If 80 becomes 92, how can you check that the answer 15% is right?
After the chapter, the learner can
- Increase 250 by 12% using the multiplier 1.12
- Find the percentage change from 80 to 92
What they copy into their notebook
Rise: multiply by 1 + the rate. Fall: multiply by 1 − the rate. Percentage change = change ÷ original × 100. Always divide by the original.