# Thread: Need to find the density

1. ## Need to find the density

Volume = 2.00 ft3 Mass = 97.5 lb Density = ? g/cm3

Can someone work this out for me please?

I am working on an example in a book and I cant seem to get the same answer.

Wondering if the book has a missprint (its probably just me though )

Thanks

$ilver 2. You need to find the density in g/cm^3. First convert mass from lb to g and volume from ft^3 to cm^3. Recall that:$\displaystyle 1~\text{ft} = 30.48~\text{cm} \implies 1~\text{ft}^3 = (30.48)^3~\text{cm}^3\displaystyle 1~\text{lb} = 453.6~\text{g}$Then find the density$\displaystyle \rho = \frac{m}{V}$. 3. Well the answer in the book says Density = 0.780896 = 0.781 g/cm3 But I dont get that answer, I get 0.195 4. The book's answer is correct. Post your work here and I (or someone else) will point out your mistake. 5. Ok thanks for that Chop Suey much appreciated, will be a few hours till I can post because I am at work atm (boss keeps walking past lol) 6. Ok this is how I tried to work it out 1ft = 30.48 cm x3 (because its cubed?) then x2 (the volume is 2.00 ft3) = 365.76 cm3 1 lb = 453.6g so 453.6 x 97.5 = 44226g Then divide mass 44226g by volume 365.76cm =120.9153543 7. Okay, it seems you are not familiar with exponents. When I said$\displaystyle (30.48)^3$, I meant$\displaystyle 30.48 \times 30.48 \times 30.48$.$\displaystyle 5^2 = 5 \times 5 = 25\displaystyle 3^4 = 3 \times 3 \times 3 \times 3 = 81\displaystyle 9^2 = 9 \times 9 = 81\displaystyle a^n = \underbrace{a \times a \times a \times \ldots \times a}_{\text{n times}}$8. Could you post the steps needed with the answers so I can see what I am doing wrong? Thanks$ilver

9. Ok no need I finaly got it.

Thanks for the help Chop Suey