Approximation and Errors

Hong Kong

Stage 1 - Stage 3

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!

Now it's your turn!

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% .

Which point on the line is closest to $95%$95%?

$A$

`A`A$D$

`D`B$C$

`C`C$B$

`B`D

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?

$10%\times454$10%×454

A$20%\times454$20%×454

B$10%\times400$10%×400

C

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.

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%

CTo 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%

CThe percentage of females between the ages of $20$20 and $29$29 is about:

$15%$15%

A$7%$7%

B$25%$25%

CThe percentage of males below $20$20 years of age is about:

$15%$15%

A$10%$10%

B$30%$30%

C$50%$50%

D