Question

Here is a rectangle ABCD.

A
B
20 cm
30 cm
The length of the rectangle is increased by 10%.
The width of the rectangle is increased by 5%.
Find the percentage increase in the perimeter of the rectangle.

Answer 1

Answer: 8%

Explanation:

Original Perimeter of the rectangle is:

= 2 * ( Length * Width)

= 2 * (20 + 30)

= 100 cm

The length increased by 10%. It therefore increased to:

= 30 * ( 1 + 10%)

= 30 * 1.1

= 33 cm

The width increased by 5%. It increased to:

= 20 * ( 1 + 5%)

= 21 cm

New Perimeter is therefore:

= 2 * ( 33 + 21)

= 108 cm

Percentage increase in perimeter is:

= (New perimeter - old) / old perimeter

= (108 - 100) / 100

= 8%