Let
x====> the circumference in inches
y ----> safe working load in pounds
Remember that
A relationship between two variables, x, and y, represent a proportional variation if it can be expressed in the form
y=Kx
where
K is the constant of proportionality
K=y/x
Verify if we have a proportional variation
For x=1, y=180 -----> k=180/1=180
For x=2, y=720 ----> k=720/2=360
For x=3, y=1620 ----> k=1620/3=540
is not a proportional relationship
so
we have the sequence
x=1 -----> y=180
x=2 ----> y=180(4)=720 -----> the factor is 2x
x=3 ----> y=180(9)=1620 ----> the factor is 3x
y=180x^2
Verify
For x=1 -----> y=180(1^2)=180 is ok
For x=2 ----> y=180(2^2)=720 is ok
For x=3 ----> y=180(3^2)=1620 is ok
therefore
For x=10 in
y=180(10^2)=1800 pounds
the answer is 1,800 pounds