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What's the proper way to solve this problem?

Quote:If a car uses 1 1/2 gallons of gas every 30 miles, how many miles can be driven with 6 gallons of gas?

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divide

6 gal/1.5 gal=4 gal

multiply

4 gal x 30 miles=120 miles

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Alram is correct. Another way to think about it:

If the car goes 30 miles in 1.5 hours, you can double both those numbers to get 60 miles in 3 hours. Then double again to get 120 miles in 6 hours.

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alram Wrote:divide

6 gal/1.5 gal=4 gal

multiply

4 gal x 30 miles=120 miles

Thanks!

KayV Wrote:Alram is correct. Another way to think about it:

If the car goes 30 miles in 1.5 hours, you can double both those numbers to get 60 miles in 3 hours. Then double again to get 120 miles in 6 hours.

You guys are awesome! The qualifying test that I'm studying for will be timed and little "tricks" like this will help!

If you don't mind, I have another basic algebra question:

Quote:An airplane flying a distance of 875 miles used 70 gallons of gasoline. How many gallons will it need to travel 3000 miles?

I believe it's something like this, but I can't remember how to manipulate it into a solvable equation:

875/70 = 3000/x

Can you run me through this step-by-step?

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06-29-2014, 05:13 PM
(This post was last modified: 06-29-2014, 05:16 PM by bluebooger.)
cross multiply

just keep your units the same (gallons, miles, grams, light years,

keep them the same and it all works out

Code:

`(1.5/30) = (6/x)`

1.5 gallons 6 gallons

------------ = ----------

30 miles x miles

1.5 * x = 30 * 6

1.5 * x = 180

x = 180/1.5

x = 120

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06-29-2014, 05:25 PM
(This post was last modified: 06-29-2014, 05:28 PM by Lindagerr.)
bluebooger Wrote:cross multiply

just keep your units the same (gallons, miles, grams, light years,

keep them the same and it all works out

Code:

`(1.5/30) = (6/x)`

1.5 gallons 6 gallons

------------ = ----------

30 miles x miles

1.5 * x = 30 * 6

1.5 * x = 180

x = 180/1.5

x = 120

You can do the same for your last question

cross multiply and divide

875 whatnot 3000 whatnot

------ = ------

70 thingies x thingies

3000 X 70 = 210,000

210,000 divided by 875 = 240

X = 240

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