Question

2. Carissa also has a sink that is shaped like a half-sphere. The sink has a volume of 2000/3 pi in^3 . One day, her sink clogged. She has to use one of two conical cups to scoop the water out of the sink. The sink is completely full when Carissa begins scooping.
(a) One cup has a diameter of 4 in. and a height of 8 in. How many cups of water must Carissa scoop out of the sink with this cup to empty it? Round the number of scoops to the nearest whole number.
I got the answer 62.5 and then rounded to 63 cups.

(b) One cup has a diameter of 8 in. and a height of 8 in. How many cups of water must she scoop out of the sink with this cup to empty it? Round the number of scoops to the nearest whole number.
I got 15.625 and rounded to 16 cups.

Are these answers correct?

Answer 1

Yes, your answers are correct.

The volume of a cone is given by V = 1/3πr²h.  Since the diameter of the first cone is 4, the radius is 2; therefore the volume is

V = 1/3π(2²)(8) = 32π/3

We divide the volume of the sink, 2000π/3, by the volume of the cone:

2000π/3 ÷ 32π/3 = 2000π/3 × 3/32π = 6000π/96π = 62.5 ≈ 63.

The diameter of the second conical cup is 8, so the radius is 4.  The volume then is:

V = 1/3π(4²)(8) = 128π/3

Dividing the volume of the sink, 2000π/3, by 128π/3:

2000π/3 ÷ 128π/3 = 2000π/3 × 3/128π = 6000π/384π = 15.625 ≈ 16