## richardlong369 3 years ago Find surface Area & Volume of the regular pentagonal pyramid ------> Click on Attachment

1. richardlong369

2. Mertsj

First find the area of the base. The formula is 1/2(perimeter)(apothem)

3. Mertsj

Find that and tell me what you get.

4. richardlong369

177.975

5. Mertsj

Yes. That's what I got.

6. Mertsj

Not we have to find the area of one of those triangles and multiply by 5. I'll draw a picture. We know the base is 10.17 and the slant height is the height of the triangle.

7. Mertsj

|dw:1339278986157:dw|

8. Mertsj

Find the area of that triangle and multiply it by 5

9. richardlong369

127.125

10. Mertsj

Is that one triangle or all 5?

11. richardlong369

one

12. richardlong369

5 would be 635.625

13. Mertsj

Now add the area of the base that we calculated earlier. That should be the total surface area.

14. richardlong369

SA = 762.75 ?

15. Mertsj

What is the area of the base?

16. richardlong369

50.85

17. richardlong369

i mean 635.625

18. Mertsj

What is the area of the 5 triangles?

19. richardlong369

635.625

20. Mertsj

First find the area of the base. The formula is 1/2(perimeter)(apothem)12 minutes ago •Report Abuse Delete 99 Mertsj 0Find that and tell me what you get.11 minutes ago •Report Abuse Delete 43 richardlong369 Best Answer 0177.975

21. Mertsj

If you look back through the posts you will find the area of the base and the area of the 5 triangles. Add them together to get the total area.

22. richardlong369

813.6

23. Mertsj

yes. That is the surface area.

24. Mertsj

Now the volume. Fortunately we are partly done with the volume because we already know the area of the base.

25. Mertsj

So find that number. The area of the base. To find the volume multiply these 3 numbers: 1/3, the area of the base, and the height of the pyramid which is shown in the picture to be what?

26. richardlong369

i got 13361.486

27. Mertsj

What is the height?

28. richardlong369

25

29. Mertsj

That's the slant height. Look at the picture.

30. richardlong369

24

31. richardlong369

its 24

32. Mertsj

The slant height is the height of the triangles that make the pyramid.

33. Mertsj

Yes. 1/3(24)=8 so multiply 8 times the area of the base. What do you get?

34. richardlong369

1423.8

35. Mertsj

That's what I got as well. That would be m^3

36. richardlong369

thankyou

37. Mertsj

yw