Percentages and Discounts
Solve problems that require finding a familiar fraction, decimal or percentage of a quantity, including percentage discounts, choosing efficient calculation strategies.
Read this first
Per cent means out of a hundred. Find 10% first and everything else follows.
25 shaded out of 100 is 25%, which is a quarter.
Words you need
- Per cent
- Out of a hundred.
- Discount
- An amount taken off the price.
- Quantity
- The amount you are working with.
Worked example
e.g. Find 15% of $60.
- Find 10% first. Divide by 10. That is $6.
- Find 5%. That is half of 10%, so $3.
- Add them. 10% plus 5% is 15%.
- 3 = 60 is $9.
For a discount, work out the saving, then take it off the price.
Practice
The pictures fade as you go. By the last few you are on your own.
1What is 50% of 80?with a picture
Answer40.
2What is 25% of 40?with a picture
Answer10.
3What is 20% of 150?with a hint
Need a hint?
Find 10% first, then double it.
Answer30.
4A $40 shirt has 25% off. What do you pay?with a hint
Need a hint?
Find the saving, then subtract.
Answer$30.
5What is 5% of 200?on your own
Answer10.
6A $90 bag has 10% off. What is the new price?on your own
Answer$81.
7Which is more: 50% of 60, or 25% of 100?on your own
AnswerThey are equal. Both are 30 and 25.
Think about it
1
Why is 10% so useful?
One good answerDividing by 10 is easy, and everything builds from it.
2
Is 50% always the same amount?
One good answerNo. It depends what you take it from.
Common mistakes
Taking the percentage off the wrong number.
Always take it from the original price.
Thinking 25% off means you pay 25%.
You pay 75%.