## kenialove one year ago A cone has a height of 24 inches , a slant height of 25 inches , and a diameter of 14 inches. What is the surface area of the cone ? A. 1,176 pi^2 B. 392 pi^2 C. 224 pi^2 D. 178 pi^2 I know how to plug in the numbers and everything but I forgot the formula to find my answer .. Can someone help me ?

1. jim_thompson5910

The surface area of a cone is $\Large SA = \pi*r^2 + \pi*r*s$ SA = surface area r = radius s = slant height

2. jim_thompson5910

In this problem, r = 7 since the diameter is 14 and you cut the diameter in half to get the radius. Also, s = 25 is the slant height.

3. kenialove

Thanks so much

4. kenialove

So it would be .. A = 3.14 x 7^2 + 3.14 x 7 x 25

5. kenialove

I got the answer 703.36 but that's not one of the choices in the question .. Can u help me ? @jim_thompson5910

6. jim_thompson5910

leave pi as it is

7. jim_thompson5910

think of pi as a variable if you have to

8. kenialove

Okay I'll try that

9. jim_thompson5910

tell me what you get

10. kenialove

I think I need help cause I'm getting a bigger number

11. jim_thompson5910

what is 7^2 equal to?

12. kenialove

49

13. jim_thompson5910

how about 7*25, what is that equal to?

14. kenialove

175

15. jim_thompson5910

So... $\Large SA = \pi*r^2 + \pi*r*s$ $\Large SA = \pi*7^2 + \pi*7*25$ $\Large SA = \pi*49 + \pi*175$ $\Large SA = 49\pi + 175\pi$ $\Large SA = 224\pi$

16. jim_thompson5910

notice how I added 49pi to 175pi to get 224pi similar to me saying 49x+175x = 224x

17. kenialove

Ohhh I know where I missed up Thanks so much

18. jim_thompson5910