## ErinWeeks 2 years ago Find the surface area of the cone to the nearest tenth.

1. ErinWeeks

2. ErinWeeks

A. 203 cm2 B. 1341.5 cm2 C. 747.7 cm2 D. 213.5 cm2

3. phi

4. phi

can you match your numbers to the variable names in the formula?

5. ErinWeeks

i got 441 pi but thats not right..

6. ErinWeeks

i did 1/3 pi 7^2 27 .. what did i do wrong?

7. ErinWeeks

ooops i did the volume formula thats why!

8. ErinWeeks

this time i got 238 thats still not right ...

9. phi

$area = \pi r^2 + \pi r s$ r is 7 and s is 27 is that what you started with ?

10. phi

it looks like you did not multiply by pi

11. ErinWeeks

im still getting 238 -_-

12. ErinWeeks

i did pi*7^2 + pi 7 * 27

13. phi

238 is r^2 + r*s the formula is pi r^2 + pi*r*s or pi*(r^2 + r*s)

14. phi

7*7 is 49 7*27 is 189 add together you get 238 no pi

15. phi

can you figure out how to do it?

16. ErinWeeks

okay i get that

17. ErinWeeks

for pi * 7^2 i got 153.86

18. ErinWeeks

for pi * 7 * 27 i got 593.46

19. ErinWeeks

so would it be C ???

20. phi

yes, I thought you figured it out already.

21. ErinWeeks

okay so it is C?

22. phi

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

23. ErinWeeks

okay thank you so much for your help!!!

24. phi

yw