40% of the pupils in a school walk to school. That's 240 pupils. How many pupils are in the school?
There are 600 pupils in the school.
Ans: 600
Example 1
The pie chart shows the drinks sold at a school stall. The part for Milk is a right angle. 125 cartons of milk were sold. How many drinks were sold in all?
500 drinks were sold in all.
Ans: 500
How to solve it
Draw the whole as one bar and mark it with a question mark. The whole is 100 percent.
Show the part: 40 percent is 240 pupils. The 240 came with a percentage, so it is a part of the school, not the whole.
Go down to 1 percent by dividing: 240 divided by 40 is 6 pupils.
Go up to 100 percent: 100 times 6 is 600 pupils.
If the percentage is hidden in a pie chart, find it first: a right angle is 90 out of 360, one quarter, so 25 percent.
The percentage is the part over the whole, times 100 percent. Then down to 1 percent, and up to 100 percent.
Practice questions with worked solutions
Questions 1 and 9 are free to try. The other 7 open in the free trial, each with its full working.
Question 9 of 9 · Intermediate · free to tryA pie chart shows the drinks sold at a school stall. The part for milk is a…A pie chart shows the drinks…
A pie chart shows the drinks sold at a school stall. The part for milk is a right angle. 125 cartons of milk were sold. How many drinks were sold in all?
Show the working and the answer
Working
percentage = part/whole × 100%
90/360 = 1/4 × 100% = 25%
25% → 125
1% → 125 ÷ 25 = 5
100% → 100 × 5 = 500
Answer: 500
For parents
What is the method for finding the whole from a percentage in P6?
This is one of the two new Primary 6 percentage outcomes: given a part and the percentage it stands for, find the whole.
What your child learns here
This is one of the two new Primary 6 percentage outcomes: given a part and the percentage it stands for, find the whole. It also covers finding an original amount after an increase or a decrease, by working back from the new percentage.
Find the whole given a part and its percentage, through the value of 1%.
Find the original amount after a percentage increase or decrease, starting from the new percentage.
Read a percentage from a pie chart before using it.
Check that the whole comes out bigger than the part.
Does the answer make sense?
The whole must be bigger than any part of it, so your child's number of seats in the hall must be more than the 340 filled. After an increase, though, the amount at the start is the smaller one: the bamboo plant must have been shorter last month than it is now.
How to practise these questions
Basic questions train finding the whole from one part and its percentage. Intermediate questions add values after an increase or decrease, a difference of two percentages, and pie charts labelled in mixed forms. If finding the whole from a part stalls, read the written step-by-step solution.
Questions parents ask
Is finding the whole from a percentage a P6 topic? Yes. 'Finding the whole given a part and the percentage' is outcome 1.1 of the Primary 6 Percentage sub-strand in the MOE syllabus.
Why go down to 1% first? Because 1% is easy to scale up. If 40% is 240, then 1% is 6 and 100% is 600, and the same steps work for any percentage.
How do you find the original price after a discount? The price paid is 100% minus the discount. If an item cost $45 after 10% off, $45 is 90% of the original, so 1% is 50 cents and the original price was $50.
