Question

Maths

Last year Gill’s cylindrical 21st birthday cake wasn’t big enough to feed all her friends. This year she will double the radius and triple the height. What will be the ratio of the volume of this year’s birthday cake to the volume of last year’s cake?

Answer 1

• 12 : 1

Explanation:

The volume of a cylinder:

• V = πr²h, where r-radius, h-height

New dimensions of the cake:

• r1 → 2r and h1→ 3h

The volume of the bigger cake:

• V1 = π*(2r)²*(3h) = 12*πr²h = 12V
• V1/V = 12

The ration of volumes is 12 : 1