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

Given :-

• Perimeter of a rectangular box = 80 cm
• Length of rectangular box is 4 more than its breadth.
• Breadth of rectangular box = x cm

To find :-

• Length of Rectangular box?

Solution:

Length of rectangular box is 4 more than its breadth. So,

☯ If length of rectangular box is x cm.

☯ Then, breadth of rectangular box is (3x + 4) cm

Here,

• Perimeter of a rectangular box = 80 cm

We know that,

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

Now, According to the Question:

➻ 2(x + (3x + 4)) = 80

➻ 2(4x + 4) = 80

➻ 4x + 4 = 80/2

➻ 4x + 4 = 40

➻ 4(x + 1) = 40

➻ x + 1 = 40/4

➻ x + 1 = 10

➻ x = 10 - 1

➻ x = 9

Therefore,

• Breadth of rectangular box, x = 9 cm
• Length of rectangular box, (3x + 4) = 3 × 9 + 4 = 27 + 4 = 31 cm

∴ Hence, Length of rectangular box is 31 cm.