In a mixture of concrete, there are four lb of cement mix for each pound of gravel. if the mixture contains a total of 115 lb of these two ingredients, how many pounds of gravel are there

For this case, the first thing we must do is define variables:

x: pounds of gravel

y: pounds of cement

We now write the system of equations:

x + y = 115

y = 4x

Solving the system of equations we have:

x = 23

y = 92

Answer:

there are 23 pounds of gravel