# Thread: Need help to calculate for height for a cylinder.

1. ## Need help to calculate for height for a cylinder.

Need help with home work.
What length of 71 cm in diameter(inside) pipe is required to make a water storage tank with a capacity of 94 litres?
What is the length in cm???
I am having trouble with this one.
Joanne

Need help with home work.
What length of 71 cm in diameter(inside) pipe is required to make a water storage tank with a capacity of 94 litres?
What is the length in cm???
I am having trouble with this one.
Joanne
The capacity is $\displaystyle 94\,\textrm{L} = 94\,000\,\textrm{mL}$.

So the volume is $\displaystyle 94\,000\,\textrm{cm}^3$.

You should know that the volume of a cylinder is given by the formula:

$\displaystyle V = \pi r^2 h$.

Since the diameter is $\displaystyle 71\,\textrm{cm}$ the radius is $\displaystyle 35.5\,\textrm{cm}$.

So $\displaystyle 94\,000\,\textrm{cm}^3 = \pi \left(35.5\,\textrm{cm}\right)^2 h$.

Solve for $\displaystyle h$.

3. Originally Posted by Prove It
The capacity is $\displaystyle 94\,\textrm{L} = 94\,000\,\textrm{mL}$.

So the volume is $\displaystyle 94\,000\,\textrm{cm}^3$.

You should know that the volume of a cylinder is given by the formula:

$\displaystyle V = \pi r^2 h$.

Since the diameter is $\displaystyle 71\,\textrm{cm}$ the radius is $\displaystyle 35.5\,\textrm{cm}$.

So $\displaystyle 94\,000\,\textrm{cm}^3 = \pi \left(35.5\,\textrm{cm}\right)^2 h$.

Solve for $\displaystyle h$.
THANK YOU for your help on this. I understand. I forgot you had to convert and only got half way and did not know what to do, but I do now. Appreciate it,
J