Hong Kong
Stage 1 - Stage 3

# Estimating Percentages

Lesson

A lot of the time it's hard for us to accurately calculate percentages of amounts in real life, so we'll have to estimate! Because percentages are expressed as something out of a hundred, we can also express them in diagrams of $5,10,100$5,10,100 things or more!

#### Example

Someone has been eating the brand new $10\times10$10×10 square block of chocolate! Can you figure out how much of the original chocolate block is left in percentages?

Think about the chocolate block as a fraction first

Do :We can see that there used to $10\times10=100$10×10=100 blocks of chocolate here, and now there are $67$67 blocks. So the fraction that represents how much is left of the original is $\frac{67}{100}$67100 . This is easily translated into a percentage as the denominator is already $100$100 , so the answer is $67%$67% .

#### Worked Examples

##### QUESTION 1

Which point on the line is closest to $56%$56%?

1. $A$A

A

$C$C

B

$D$D

C

$B$B

D

##### QUESTION 2

Ellie bought a $454$454 mL drink that claimed to be orange juice. In the ingredients list it said that orange juice made up $17%$17% of the drink. To estimate the amount of orange juice in the drink, which of the following would give the closest answer?

1. $10%\times454$10%×454

A

$20%\times454$20%×454

B

$10%\times400$10%×400

C

##### QUESTION 3

In a census, people are asked their gender and age. The graph shows the results: the percentage of females and males in each age group.

1. To the nearest $1%$1%, what percentage of females are between $5$5 and $9$9 years of age?

$7%$7%

A

$2%$2%

B

$11%$11%

C
2. To the nearest $1%$1%, what percentage of males are between $30$30 and $34$34 years of age?

$7%$7%

A

$4%$4%

B

$2%$2%

C
3. The percentage of females between the ages of $20$20 and $29$29 is about:

$15%$15%

A

$7%$7%

B

$25%$25%

C
4. The percentage of males below $20$20 years of age is about:

$15%$15%

A

$10%$10%

B

$30%$30%

C

$50%$50%

D