Question

Mary has 27 tests to correct. It takes her 1/9 of an hour to correct each test. How many hours will it take Mary to correct all the tests? 

Answer 1

To find the total time that Mary will spend correcting the tests,we have to multiply 27 by 1/9 using the general rule for the product of fractions:

$\frac{a}{b}\cdot\frac{c}{d}=\frac{a\cdot c}{b\cdot d}$

then, in this case we have the following:

$\begin{gathered} 27=\frac{27}{1} \\ \Rightarrow27\cdot\frac{1}{9}=\frac{27}{1}\cdot\frac{1}{9}=\frac{27}{9}=3 \end{gathered}$

therefore, Mary will spend 3 hours correcting the 27 tests