Online Course Discussion Forum

The homework grader is wrong?

 
 
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The homework grader is wrong?
by Jimmy Muren - Tuesday, 14 November 2017, 12:11 AM
 

For one of my questions "Suppose we have ball with radius 6. Suppose you cut the ball in half. What is the volume of the half ball? Use 3.14 for pi and round your answer to the nearest tenth if necessary. The grader said I was wrong with the answer of 452.2, but then provided me with this solution:

First note that the full ball has volume

43π×63=228π.43π×63=228π.
The half-ball has half the volume of the full ball, so the volume is
228π÷2=114π358.228π÷2=114π≈358.

The correct answer is: 358
That clearly cannot be correct because 

6^3 is 216 

216(4/3) = 288

and 288/2 = 144

so the answer should be 144(3.14) = 452.16 rounded up to 452.2 right?

 
Picture of John Lensmire
Re: The homework grader is wrong?
by John Lensmire - Tuesday, 14 November 2017, 9:43 AM
 

Hi Jimmy,

Thanks for pointing this out. Fixed and updated.