it costs $5 to mow a rectangular field 40m long and 25m wide

Geometric formulae, word problems, theorems and proofs, etc.
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little_dragon
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it costs $5 to mow a rectangular field 40m long and 25m wide

Postby little_dragon » Mon Feb 02, 2009 7:50 pm

It costs $5.00 to mo a rectangular field 40 m long and 25 m wide. How much will it cost to mow a similar field 67.5 m wide at the same rate?

I know I'm supposed to use similar figures and ratios. I get (40 m)(25 m) = 1000 m^2 for $5, so $0.005/m^2. The similar rectangles are 40-by-25 and 67.5-by-x, so using ratios gives me x = 42.1875. The area of the similar field is (67.5 m)(42.1875 m) = 2847.65625 m^2, so the cost is about $14.24. But this is wrong?

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stapel_eliz
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Postby stapel_eliz » Mon Feb 02, 2009 11:25 pm

little_dragon wrote:It costs $5.00 to mo a rectangular field 40 m long and 25 m wide. How much will it cost to mow a similar field 67.5 m wide at the same rate?

I think you crossed the dimensions...? :oops:

You appear to have used the ratio 40/25 = 67.5/x. I believe you should have:

. . . . .length : width = 40 : 25 = x : 67.5

Try it again using the ratio 40/25 = x/67.5. :wink:

Eliz.

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little_dragon
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Re: it costs $5 to mow a rectangular field 40m long and 25m wide

Postby little_dragon » Fri Feb 06, 2009 1:44 am

D'oh! Thanks! :wave:

alex61292
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Re: it costs $5 to mow a rectangular field 40m long and 25m wide

Postby alex61292 » Mon Apr 06, 2009 10:21 pm

What you are going to do is set up a proportion.
Length:Width
So you set up the proportion: 40/25 = x/67.5
that should hep you out :]


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