Question

what is the perimeter of a rectangle if it's length is doubled and breadth remains the same

Answer 1

let the length =2x
breadth =x
perimeter of rectangle =2(length+breadth)
=2(2x+x)
=2×3x
= 6x

Answer 2

Let's check.

Perimeter of rectangle = 2(l+b)= 2l +2b

Now,

Perimeter of triangle by doubling length = 2(2l+b) = 4l+ 2b

i.e. there is an increment of twice the length value in perimeter.