UP Police Constable Exam Model Paper 4

Given:
Area of rectangle increases 1 ¼ time
Length = 20 cm
Area = 320 cm${}^2$
Calculaiton:
Let the breadth of the rectangle be b. Hence we have
Area = 320 = 20 × b
⇒ b = 16 cm
its area increases 1 ¼ time i.e. 1 + 1/4 = 5/4 times
⇒ New area = 320 × 5/4 = 400 cm${}^2$
Since the breadth has not changed, we have only a change in length. Let the new length be L
⇒ L × 16 = 400
⇒ L = 25 cm
Perimeter of rectangle = 2(new length + breadth)
New perimeter = 2(25 + 16) = 82 cm