Question

My rectangular soccer field site has a length equal to three times its width. find its area in terms of its length x.

Answer 1

A rectangle with dimensions:

length = a units, and width= b units, has area: $Area=a \cdot b=ab$ (units squared)

In the rectangular soccer field, the length is x units, which may be meters, feet etc. 

and the length is 3 times the width, so the width is just one third of the length, that is width= x/3  

$Area_{field}=width \cdot length= \frac{x}{3} \cdot x= \frac{ x^{2} }{3}$  square units



Answer: $\frac{ x^{2} }{3}$ square units