Mathematics

Grade9

Easy

Question

# A sign made of solid wood is in the shape of a pyramid. The base is a triangle with a base of 6 feet and a height of 4 feet. The height of the sign is 7 feet. The wood costs $3 per cubic foot. Find the cost of the sign.

- $168
- $56
- $84
- $28

Hint:

### Volume is the product of base area and height.

## The correct answer is: $84

### Given:

a base of a pyramid b = 6 feet

a height of a pyramid h = 4 feet

To find:

Cost of the sign made of solid wood in the shape of a pyramid =?

Solution:

A sign is made up of solid wood in the shape of a pyramid.

The base of a triangle is 6 feet and the height is 4 feet.

The height of the wooden sign is 7 feet.

Suppose the V, h, l, and b be the volume, height, base length, and base width of the pyramid.

The volume of a pyramid is given by the formula,

V = 6 4 7

V = 56 feet^{3}

But The wood costs $3 per cubic foot.

Suppose T is the total cost of the sign.

T = 56 3

T = $168

So the correct option is b.

First, we can calculate the base area and then multiply it by height.