Weight

[Guest]

A tank is 8 3/4 ft. in diameter and 28 ft. in length.

The tank is a cylinder and is 2/3 full of petroleum.

Specific gravity of petroleum is .7 (7 times heavier than water).

Compute weight of petroleum.

Volume of cylinder: pi * r^2 * height or length.

3.1416 * 4.375 * 4.375 * 28 = 1683.70125 = 1684 cu. ft.

1684 * 2/3 = 1122.66666 = 1123 cu. ft.

1 cu. ft. of water weighs 62.5 lbs.

1123 * 62.5 * .7 = 49131.25 = 49131 lbs.

What parts are correct?

[Guest]

Please reply. Thanks.

[HallsofIvy]

I get 49108 by keeping several decimal places and only rounding to an integer at the end. So, for example, for the volume of the tank I get 1683.697 cubic feet rather than your "1684". 2/3 of that is 1122.465 rather than your "1123". Multiplying 1122.465 by 62.5 gives 70154.055 and 0.7 of that is 49107.838 which, to the nearest pound is 49108,

(There is one typo: you say "Specific gravity of petroleum is .7 (7 times heavier than water)." The parenthetical should be "0.7 (not 7) as heavy as water". But you used 0.7, not 7, when doing the calculation. Also, according to this: https://hypertextbook.com/facts/2007/ArtemGindin.shtml, the very lightest petroleum has specific gravity 0.8, not 0.7. Were you given that figure in the problem?)

[Guest]

Yes, .7