Question

Christopher attempted $30\%$ questions on his last math exam correctly. If there were 50 questions on the test, how many questions did he attempt correctly?

Answer 1

Question attempted correctly by Christopher
$=30\%\text{of}50$

$\because$ A percent is 1 part out of 100.
$\Rightarrow 1\%=\frac{1}{100}$
$\therefore 30\%=30\times \frac{1}{100}=\frac{30}{1}\times \frac{1}{100}=\frac{30\times 1}{1\times 100}=\frac{30}{100}$

$\therefore 30\%\text{of}50=\frac{30}{100}\times 50$
$=\frac{30\times 50}{100}$
Simplifying the fraction, we get
$=\frac{2\times 15\times 50}{50\times 2}$
Cancel out common factors, we get
$=15$

Hence, Christopher attempted 15 out of 50 questions