Question 1030336
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In a mixture of concrete, there are five lb of cement mix for each pound of gravel. 
If the mixture contains a total of 90 lb of these two ingredients, how many pounds of gravel are there?
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Group (mentally) 5 lb of cement with 1 pound of gravel.
You will get groups of cement-gravel of total weight 6 pounds each.

The number of groups is {{{90/6}}} = 15.

So, there are 15 lb of gravel in the mixture.
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