9. The length of a rectangle is 2p cm and its breadth is p cm. When the length of the rectangle is increased by 25% and the breadth is decreased by 25%, determine the percentage change in (i) its perimeter, (ii) its area. ​

Respuesta :

Answer:

The answers are:
(i) 108.33%
(ii) 93.75%

Step-by-step explanation:

The original area and perimeter are as follow:

Perimeter = 2l + 2w
                = 2(2p) + 2(p)
                = 4p + 2p
                = 6p cm

Area = l * w
        = 2p * p
        = 2p^2 cm^2

A 25% increase of the length is = 2p * (1 + 25%) = 2p * 1.25 = 2.5p cm

A 25% decrease of the breadth is = p * (1 - 25%) = p * 0.75 = 0.75p cm

Perimeter
= 2l + 2w
                 = 2(2.5p) + 2(0.75p)
                 = 5p + 1.5p
                 = 6.5p cm

Area = l * w
        = 2.5p * 0.75p
        = 1.875p^2 cm^2

Now that we have found the changes, let's calculate the percentage changes


Percentage change of perimeter:

x% * 6p = 6.5p
x/100 * 6p = 6.5p
x * 6p = 6.5p * 100
x = 650p/6p
x = 108.33

Percentage change of area:

x% * 2p^2 cm^2 = 1.875p^2 cm^2
x/100 * 2p^2 cm^2 = 1.875p^2 cm^2
x * 2p^2 cm^2 = 1.875p^2 cm^2 * 100
x = 187.5p^2 cm^2 / 2p^2 cm^2
x = 93.75