Question

A substance X has the density of 0.359 g/mL at room temperature. What is the volume in mL of 25.0 g of the substance? Show calculation.
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I tried to cross multiply but I dunno...I'm getting some pretty crazy numbers. Any suggestions?

Answer 1

25.0 grams (1 mL/ .359 grams) = 69.6 mL

Answer 2

I am not a fan of "cross multiplication and make the following suggestion:

One by any other name is one, and if you multiply by one, you do not change the amount of whatever but only its name.

for example if there are 25 cows per 3 fields I write that as (25 cows/3 fields) and since that is the same top and bottom, I name that conversion factor one :)

Now if I have 15 fields, how many cows. Multiply by my conversion factor so the units I want to cancel will cancel


now if I have 75 cows:

75 cows * ( 3 fields / 25 cows ) = 9 fields

I multiplied by fields over cows so I canceled cows and ended up with fields.

Now if I had 12 fields and wanted to know how many cows I would do the inverse:

12 fields * (25 cows /3 fields) = 100 cows

This is particularly helpful if you have a long string of conversions to make at once. It does not matter how many times you multiply by something that is the same on the top and the bottom except for the name.

Answer 3

Did you get 125 cows in 15 fields ? :)

Answer 4

yes i did thanx!
the cross multiplying actually worked out pretty well! thank u so much!