UK Secondary (7-11)
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Estimating Percentages I
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!

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 $95%$95%?

  1. $A$A

    A

    $D$D

    B

    $C$C

    C

    $B$B

    D

    $A$A

    A

    $D$D

    B

    $C$C

    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

    $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

    $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

    $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

    $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

    $15%$15%

    A

    $10%$10%

    B

    $30%$30%

    C

    $50%$50%

    D

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