##### Math word problem help needed

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If 3 bulldozers can load 5 trucks full of earth in 30 minutes, then how long should it take 5 bulldozers to load 7 trucks full of earth? Assume that all the bulldozers work equally hard and all truck loads are the same size. Solve the problem, explaining your reasoning.

Oct 28th, 2015

Let x = the number of trucks full of earth in 30 minutes

Then to determine how many trucks full of earth 5 bulldozers can load

3/5 = 5/x

Solve for x:

3x = 25

x = 25/3 trucks full of earth in 30 minutes or 25/90 per minute

7 divided by 25/90 = 630/25 = 25.2 minutes

Oct 28th, 2015

Is it possibly for you to explain each step? I'm just a little confused. Thanks!

Oct 28th, 2015

The relationship of the number of bulldozers to the number of trucks full of earth are directly proportional, so

3/5 = 5/x   where x is the number of trucks full of earth that 5 bulldozers can load.

Solving for x we get 25/3 trucks full of earth in 30 minute

Dividing by 30 we find the number of trucks fill per minute, which in this case is 25/3 / 30 = 25/90 trucks full per minute

Then,

7 trucks / 25/90 trucks/min = 25.2 minutes

Oct 28th, 2015

Thank you!

Oct 28th, 2015

Any time.

Oct 28th, 2015

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Oct 28th, 2015
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Oct 28th, 2015
Oct 17th, 2017
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