# Homework Help: 150 yd3 of water - what is the mass in pounds of water?

1. Sep 29, 2009

### master c

Hi all,

I do hope I have chosen the right forum thread to ask this question. I don't want to waste anyones time. I am trying to help guide my girlfriend with some physics questions with not much luck. One question that we are struggling with is:

A typical backyard swimming pool holds 150yd3 of water.

What is the mass in pounds of water?

So I believe you would do 150 cubed which is 150 x 150 x 150 = 3375000 yards of water in the pool - am i correct? However from there I am lost in regards to working out what the mass in pounds of water is?

Many thanks to anyone in advance which can guide us through breaking down and answering such a question.

2. Sep 29, 2009

### JasonGodbout

You have to multiply the volume with the density ($$\rho$$)

Volume x $$\rho$$ = mass

3. Sep 29, 2009

### DaveC426913

No.

Math learning is first about intuiting the answer. Intuitively, have you ever seen a pool that is 150 yards long and wide, and 150 yards deep?

This should tell you there's something wrong with your first assumption.

What is the volume of this pool?

4. Sep 29, 2009

### turbo

A typical 3-axle dump truck holds nearly 15 cubic yards of material, so how many of those would you need to be equivalent to the volume of your swimming pool? Can you visualize that?

It's pretty easy to find out what the weight of a cubic foot of water weighs, so how many cubic feet in a cubic yard, and what can you get for the weight of a cubic yard of water?

Take a stab at the calculation, so we can see if you understand the problem, and if not, why not.