# What is the volume of a tank that is 8 ft in diameter and 15 ft high?

1. Dec 21, 2014

### jim1174

1. The problem statement, all variables and given/known data
What is the volume of a tank that is 8 ft in diameter and 15 feet high

2. Relevant equations

3. The attempt at a solution
Π x (4ft) 2 x 20ft

3.14 X 24ft x 15ft = 1130.4

Last edited: Dec 21, 2014
2. Dec 21, 2014

### SteamKing

Staff Emeritus
It's not clear where the figures 13.4 and 24 come from. Also, the word 'diameter' implies that the tank is a cylinder.

3. Dec 21, 2014

### jim1174

D = diameter = 8 ft
h = height = 15 ft
A = cross-sectional area = to be determined
V = volume = to be determined

A = πD²/4
A = (3.14)(8 ft)²/4
A = 50.3 ft²

V = Ah
V = (50.3 ft²)(15 ft)
V = 754 ft³

4. Dec 21, 2014

### SteamKing

Staff Emeritus
This looks good.

5. Dec 21, 2014

### Ray Vickson

I hope you realize that 3.14 is not the value of $\pi$, but is just a 3-digit approximation to the true value (and which is sometimes close enough in some problems, but not nearly accurate enough in some other cases).

6. Dec 21, 2014

### Staff: Mentor

Just to clarify your initial work, in your first expression above, you have 20 ft where it should have been 15 ft. I understand that "(4ft) 2" is supposed to be 42, which can also be written as 4^2.

In your second expression you corrected the 20ft dimension, but 4 X 4 $\neq$ 24.

7. Dec 22, 2014

### jim1174

ok i think i got it

D = diameter = 8 ft
h = height = 15 ft
A = cross-sectional area = to be determined
V = volume = to be determined

A = πD²/4
A = (3.14) (8 ft) ²/4
A = 50.24 ft²

V = Ah
V = (50.24 ft²) (15 ft)
Volume V = 753.6 ft³

Final Answer is = V = 753.6 ft³