Question

Perimeter of a rectangular box is 80 cm . Its length is 4 cm more than 3 times its breadth.
(i) If its breadth is x cm , find its length in terms of x.

Answer 1

Answer:

Let, length of a rectangle is x and breadth is y.

As per condition 1 ie., Length of a rectangle is 4 cm more than its breadth.

The equation is,

x=y+4

∴x−y=4

As per condition 2 i.e., perimeter of the rectangle is 40 cm.

The equation is,

x+x+y+y=40

∴x+y=20

Answer 2

Answer :

›»› The length of a rectangular box is 31 cm.

Given :

• Perimeter of a rectangular box is 80 cm . Its length is 4 cm more than 3 times its breadth.

To Find :

• Length of a rectangle in terms of x.

Solution :

Let us assume that the breadth of a rectangle is x cm.

As it is given that, length is 4 cm more than 3 times its breadth.

→ 3x + 4 cm

As we know that

→ Perimeter of rectangle = 2(l + b)

→ 80 = 2(3x + 4 + x)

→ 80 = 2(3x + x + 4)

→ 80 = 2(4x + 4)

→ 80 ÷ 2 = 4x + 4

→ 80 = 4x + 4

→ 40 - 4 = 4x

→ 36 = 4x

→ x = 36/4

→ x = 9

Therefore,

• Breadth of a rectangle = x = 9
• Length of a rectangle = 3x + 4 = 3 * 9 + 4 = 27 + 4 = 31.

Hence, the length of a rectangle is 31 cm.