find the volume of a sphere with a radius of 8

Question

Multiple Choice 

 

A 512π mm^3

B 2048/3π mm^3

C 256/3π mm^3

D 16π mm^3

Answer 1

The equation for the volume of a sphere:

      V = (4/3)πr³/3

 

This is a multiple-choice question with one correct answer.  We could either (1) compute the answer then select the correct distractor (option) or we could (2) quickly eliminate distractors until only one remains.  Let's try method (2) [note: this is a really good method for time-sensitive tests.]

 

Each distractor has π so we won't have to worry about using 3.14 in our calculations.

 

r=8 and r²=64 and r³= 512.   We want (4/3)(512).  Note that (4/3) is 1 1/3.  That eliminates A, C, and D.

 

The answer is B.

 

Just to verify: (4/3)(512) = (2048/3)

 

 

Answer 2

Hi Enrique, the formula for the volume of a sphere is: V = 4 / 3 * Pi * r³.

 

For a sphere of radius 8, the volume is:

 

V = 4 / 3 * Pi * 8³

 

V = 4 / 3 * Pi * 512

 

V = 2048 / 3 * Pi

 

Answer: B.

 

Questions?