Question

The ratio of length and breadth of a rectangular playground is 3:2. There
is a two meter wide jogging track along and outside the playground. The
total area of the track and the playground is 2816 sq.m. Find the length
and breadth of the playground,​

Answer 1

Answer:

We know that the ratio of length and breadth of a rectangular playground is 3:2

Then if the length is L, and the breadth is B, we have the relationship:

L = (3/2)*B

Outside this playground, we have a jogging track of 2m, then if we also consider the jogging track the length and breadth are:

L' = L + 2m

B' = B + 2m

The area is the product between the area and the breadth, then the area is:

A = B'*L'

A = (L + 2m)*(B + 2m)

And remember that L = (3/2)*B

Then we get:

A =  ((3/2)*B + 2m)*(B + 2m)

And the area is 2816 m^2

Then we have:

A =  ((3/2)*B + 2m)*(B + 2m) = 2816 m^2

Now we can solve the equation:

((3/2)*B + 2m)*(B + 2m) = 2816 m^2

(3/2)*B^2 + 3m*B + 2m*B + 4m^2 = 2816 m^2

(3/2)*B^2 + 5m*B =  2816 m^2 - 4m^2 = 2812m^2

Then we can write:

(3/2)*B^2 + 5m*B -  2812m^2 = 0

We can solve this if we use Bhaskara's formula:

$B = \frac{-(5m) +- \sqrt{(5m)^2 - 4*(3/2)*(-2812m^2)} }{2*(3/2)} = \frac{-5m +-130m}{3}$

One solution is negative, so we can discard that one, then we only take the positive:

B = (-5m + 130m)/3 = 41.67m

And L = (3/2)*B

L = (3/2)*40.7m = 62.5m

The breadth is 41.67 meters and the length is 62.5 meters.