SOLUTION: A concrete walkway has the following specifications: 4' wide. 1/3' thick. 3000' in length. Materials used: 1 part cement, 2 parts sand, 5 parts gravel. Determine amo

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Question 1204245: A concrete walkway has the following specifications:
4' wide.
1/3' thick.
3000' in length.
Materials used: 1 part cement, 2 parts sand, 5 parts gravel.
Determine amount (cu. ft.) of each material used.
My attempt:
Material; 1:2:5 1 + 2 + 5 = 8
Volume of walkway: 4 * .33 * 3000 = 3960 cu. ft.
Not sure from here.

Found 2 solutions by ikleyn, greenestamps:
Answer by ikleyn(52838)   (Show Source): You can put this solution on YOUR website!
.

To start, you should find the total volume. For it, you should multiply

    4 *  * 3000 = 4000 cu ft.   (not 3960, which is your value, by mistake !)



      So, the total volume of 8 equal parts is 4000 cu ft.



Next your step is to find the volume for each of 8 parts.


For it, OBVIOUSLY, you should divide 4000 by 8.


The steps that follow are so obvious that I will not go in further details.


Nevertheless, if you have questions, do not hesitate to ask.



Answer by greenestamps(13203)   (Show Source): You can put this solution on YOUR website!


Note that ".33" is not a very good decimal approximation of "1/3". Why would you use a 2-digit decimal approximation for 1/3 when the denominator of the fraction is a single digit? Fewer digits nearly always means easier arithmetic.

(4)(.33)(3000) = 4(990) = 3960 (not a very good approximation)

(4)(1/3)(3000) = 4(1000) = 4000 (exact)

In the work you show, you have the following:

1:2:5 --> 1 + 2 + 5 = 8

The standard way of using a given ratio to set up a problem for solving makes it easier to see how to finish the problem:

1:2:5 --> 1x+2x+5x=8x

Then

8x=4000

And from there it should be easy to find the values of 1x, 2x, and 5x, which are the answers to the problem.
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