Question

Let y = safe load in pounds and x = depth in inches for a certain type of rectangular horizontal beam. A constant of proportionality exists such that y = kx². Determine the constant k for a beam with y = 1,000 pounds and x = 5 inches.
A. 40
B.100
C.200

Answer 1

A. 40.  The formula y = kx² is the problem being presented y = 1,000  and x = 5. Plug in the values to solve 
1000 = k * 5^2  (square 5 to get)
1000 = k*25   
divide both sides by 25
1000/25 = 40
40 = k