ErinWeeks
Find the surface area of the cone to the nearest tenth.
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ErinWeeks
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ErinWeeks
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A. 203 cm2
B. 1341.5 cm2
C. 747.7 cm2
D. 213.5 cm2
phi
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can you match your numbers to the variable names in the formula?
ErinWeeks
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i got 441 pi but thats not right..
ErinWeeks
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i did 1/3 pi 7^2 27 .. what did i do wrong?
ErinWeeks
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ooops i did the volume formula thats why!
ErinWeeks
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this time i got 238 thats still not right ...
phi
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\[ area = \pi r^2 + \pi r s\]
r is 7 and s is 27
is that what you started with ?
phi
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it looks like you did not multiply by pi
ErinWeeks
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im still getting 238 -_-
ErinWeeks
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i did pi*7^2 + pi 7 * 27
phi
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238 is r^2 + r*s
the formula is pi r^2 + pi*r*s
or pi*(r^2 + r*s)
phi
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7*7 is 49
7*27 is 189
add together you get 238
no pi
phi
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can you figure out how to do it?
ErinWeeks
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okay i get that
ErinWeeks
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for pi * 7^2 i got 153.86
ErinWeeks
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for pi * 7 * 27 i got 593.46
ErinWeeks
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so would it be C ???
phi
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yes, I thought you figured it out already.
ErinWeeks
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okay so it is C?
phi
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btw, you should not round to only 2 decimals, because your answer is slightly off.
if you used all the digits the calculator gives you you get
747.6990516 which rounds to 747.7
ErinWeeks
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okay thank you so much for your help!!!
phi
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yw