Math CentralQuandaries & Queries


Question from Jennifer, a student:

75% of 12.5

Please explain how you got your answer cause I don't understand how to do this

Hi Jennifer,

When I first see this problem my first reaction is:

"75% is three quarters and 12.5 is a little more than 12. One quarter of 12 is 3 and hence three quarters of 12 is $3 \times 3 = 9.$"

Thus the answer to your question should be a little more than 9.

You can get the precise answer using the method I used above. 75% is $\large \frac34,$ and $\large \frac14$ of $12.5$ is $\large \frac14 \times 12.5 = \frac{12.5}{4} = 3.125.$ Hence $\large \frac34$ of $12.5$ is $3 \times 3.125.$

A second method doesn't use the fraction $\large \frac34$ but uses the 75% directly. "Per cent" means "per one hundred" so $75\% = \frac{75}{100} = 0.75.$ Hence 75% of 12.5 is $0.75 \times 12.5.$

I hope this helps,

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