Simple QR Question?

[sweetdaises2000]

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Hey guys, this is probably a really simple question, and I'm guessing maybe it has something to do with conversions when you cube numbers but please clarify-am I missing something here?
Here is the question: The Volume, V, is related to its radius r, and is given by the equation V=4/3piR^3. What is the radius in feet, of a sphere having a volume of 288 cubic feet.

Kaplan says the answer is 4. The answer choices are 3, 4,6,or 8. I'm kinda stuck here when i get to the the fact that r^3=216 ft^3 .So to get the radius, you would need the 3rd root of 216 right? I feel like I'm missing something...

 

[UCB05]

Hey guys, this is probably a really simple question, and I'm guessing maybe it has something to do with conversions when you cube numbers but please clarify-am I missing something here?
Here is the question: The Volume, V, is related to its radius r, and is given by the equation V=4/3piR^3. What is the radius in feet, of a sphere having a volume of 288 cubic feet.

Kaplan says the answer is 4. The answer choices are 3, 4,6,or 8. I'm kinda stuck here when i get to the the fact that r^3=216 ft^3 .So to get the radius, you would need the 3rd root of 216 right? I feel like I'm missing something...

You missed the pi 😛 You need to further simplify. 216=(pi)r^3 (not 216=r^3). you can therefore estimate that r^3= something a little less than 72. 3^3=27, 6^3=a bit over 200. The reasonable answer will be between them, 4.

 

[sweetdaises2000]

Thanks so much UCB! I knew it had to be something simple 🙂