# Question #09bb3

Dec 13, 2017

Perimeter of rectangle = $72$ inches.

#### Explanation:

Given: The perimeter of a rectangle is three times its length.
So, if length =$l$,
then perimeter $P$ = $3 l$------ Let this be (1).

But we know that perimeter of a rectangle is:

$P = 2 \left(l + w\right)$ ------ Let this be (2). Where $w =$ width.

Given that :width $w$ of the rectangle is 12 inches.---- Let this be (3)

We substitute values from (1) and (3) in (2):

(2)$\implies P = 2 \left(l + w\right)$

( We can also say that as the left hand side of (1) and(2) are equal, equating the right hand sides we get--)

$\implies 3 l = 2 \left(l + 12\right)$

$\implies 3 l = 2 l + 24$

$\implies 3 l - 2 l = 24$ -----by transposition.

$\implies l = 24$ inches.

Now substitute this value of $l$ in (1) or (2):

(1) $\implies P = 3 l = 3 \times 24 = 72$ inches.

$\therefore$perimeter of rectangle in inches = $72$ inches.