Dru is constructing a bridge. it takes 12 cubic yards of concrete to make a bridge that is
4 inches thick.
20. write a direct variation equation that relates c and t, where c is cubic yards of concrete and t
is thickness in inches.
also, how many cubic yards of concrete does dru need to make the bridge 6 inches thick?

c=3t is the equation

18 cubic yards of concrete is what we need for a 6 inch thick bridge.

Step-by-step explanation:

If something directly varies, that means there is a constant, k, such that when you multiply it to one variable you always get the other variable.

That is for this particular problem we have c=kt where c is cubic yards and t is thickness in inches.

So we are given from the first sentence: 12 cubic yards and 4 inches thick which means we have:

12=k(4)

Divide both sides by 4:

12/4=k

Simplify:

3=k

So the equation is c=3t for any point (c,t) in this relation.

So we want to know many cubic yards of concrete (we want to know (c) so that Dru can build a 6 inch (t) thick bridge.

c=3(6)

c=18

18 cubic yards

54

step-by-step explanation: