Home » » A frustum of a pyramid is 3cm square at the top and 6cm square at the bottom and...

# A frustum of a pyramid is 3cm square at the top and 6cm square at the bottom and...

### Question

A frustum of a pyramid is 3cm square at the top and 6cm square at the bottom and is 5cm high. The volume in cm3 of the frustum is

A) 15

B) 150

C) 105

D) 115

E) 36

## Discussion (3)

• The formula for calculating the volume of frustum= V=1 / 3(a^2+ab+b^2)h
a=3,b=6,h=5
Sub everything inside the formula and it will give u 105

• Formula for the frustum of a pyramid=⅓h ( a² + ab + b² )
Where a ( base ) = 6
Where b ( top ) = 3 and the height, h = 5.
⅓ × 5 ( 6² + 6×3 + 3² ) = 105cm³.

• Sarah

The formular is
V=h/3(A+A'+√AA'
Where V is volume
H is height
A is area of upper base
A' area of lower base
Since the frsutum is a square
The area of upper base is A^2
Which is 3×3=9
Area of the bottom also square is
6×6=36
Height =5cm (given)
We have V =5/3(9+36+√(9×36)
V=5/3(45+√324
V=5/3(45 +18)
V=5/3(63)
V=315/3
V=105cm^3