Question

area of a rectangle is 51.2 dm square and the sides are in the ratio 5 ratio 4 find its perimeter ​

Answer 1

Explanation:

let the length be 5x dm and breadth be 4x dm

$area = l \times b \\ 51.2 = 5x \times 4x \\ \frac{512 }{10} = 20 {x}^{2} \\ \frac{512}{200} = {x}^{2} \\ \frac{256}{100} = {x}^{2} \\ \sqrt{ \frac{256}{100} } = {x} \\ \frac{16}{10} = x \\ x = 1.6dm$

$l = 5x = 5(1.6) = 8 \: dm \\ b = 4x = 4(1.6) = 6.4 \: dm \\ perimeter = 2(l + b) \\ = 2(8 + 6.4) \\ = 2(14.4) \\ = 28.8 \: dm$