Question

length of rectangle is increased by 30 and breadth is increased by 20 find the percentage change in perimeter

Answer 1

Let the original Length of rectangle = x
And Breadth = y
So perimeter of original rectangle = 2(x +y)
Now
Length of new rectangle = (x+30)
And breadth = (y+20)
New perimeter = 2[(x + 30) + (y + 20)] = 2x +2y + 60 +40 = original perimeter + 100
So percent change formula is
(Change amount *100)/Original amount
Applying above formula
(100 * 100)/2(x+y) is the percent change