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Simple Math Problem - It's been a while... - NJGx03x871 - 06-29-2014

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?



Simple Math Problem - It's been a while... - alram - 06-29-2014

divide
6 gal/1.5 gal=4 gal

multiply
4 gal x 30 miles=120 miles


Simple Math Problem - It's been a while... - KayV - 06-29-2014

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.


Simple Math Problem - It's been a while... - NJGx03x871 - 06-29-2014

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?


Simple Math Problem - It's been a while... - bluebooger - 06-29-2014

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



Simple Math Problem - It's been a while... - Lindagerr - 06-29-2014

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