The following rectangle is constructed from 7 small identical rectangles whose length is 5cm. what is the perimeter of the biggest rectangle?

cm

It is easy to see that the length of the biggest rectangle is just 5 × 2 = 10cm. We see that 5 widths of the small rectangle equal the length of the large rectangle. Therefore, the width of the small rectangle is 10 ÷ 5 = 2 cm. The width of the large rectangle is therefore 5 + 2 = 7 cm. The perimeter of the large rectangle is therefore 10 + 10 + 10 + 7 = 34 cm.