Problema Solution
The cost of copper tubing varies jointly as the length and diameter of the tubing. If 20 feet of 1/2 inch diameter tubing costs $36.60, then what is the cost of 100 feet of 3/4 inch diameter tubing?
Answer provided by our tutors
the cost c varies jointly as the length l and and diameter d means
c = k*l*d, where k is a constant of variation
for l = 20 ft and d = 1/2 in = (1/2)(1/12) ft = 1/24 ft (1ft = 12 in => 1 in = (1/12) ft)
c = $36.60
36.60 = k*20*(1/24)
by solving we find
k = 43.92
click here to see the step by step solution of the equation
now for l = 100 ft and d = 3/4 in = (3/4)(1/12) ft we have
c = 43.92*100*(3/4)(1/12)
c = $274.5
the cost of 100 feet of 3/4 inch diameter tubing is $274.5.