Question

Thomas bought 12 rectangular grass beds measuring 9 cm by 5 cm. When he arranged them on his lawn, 5 beds were left unused. Find the area of the lawn.

• A. 45 cm${}^2$
• B. 225 cm${}^2$
• C. 315 cm${}^2$
• D. 540 cm${}^2$

Answer 1

The correct option is C 315 cm${}^2$

Area of lawn
= Area of 12 grass bed - Area of 5 grass beds

Area of rectangular grass bed
= length x breadth
= $(9\times 5)c{m}^2$

So, area of 12 grass beds $=12(9\times 5)c{m}^2$
and, area of 5 grass beds $=5(9\times 5)c{m}^2$

Area of lawn
= $12(9\times 5)-5(9\times 5)$
= $(12-5)\times 9\times 5$
= $7\times 9\times 5$
= $7\times 45$
= $315c{m}^2$

Therefore, area of the lawn is 315 $c{m}^2$.