Question

Walter takes 7/10 of an hour to mow 2/5 of an acre of lawn. At this rate, how many acres will he mow in an hour?

Answer 1

4/7 acres per hour

Explanation:

Answer 2

`\bf \begin{array}{ccll} hours&\stackrel{lawn}{acre}\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ (7)/(10)&(2)/(5)\\\\ 1&a \end{array}\implies \cfrac{(7)/(10)}{1}=\cfrac{(2)/(5)}{a}\implies \cfrac{(7)/(10)}{(1)/(1)}=\cfrac{(2)/(5)}{(a)/(1)}\implies \cfrac{7}{10}\cdot \cfrac{1}{1}=\cfrac{2}{5}\cdot \cfrac{1}{a} \\\\\\ \cfrac{7}{10}=\cfrac{2}{5a}\implies 35a=20\implies a=\cfrac{20}{35}\implies a=\cfrac{4}{7}`