Question

What is the constant of proportionality of a graph if x equals 3 and y equals 90?

Answer 1

y = kx

'k' is the constant of proportionality, or otherwise known as constant of variation. 

y = 90
x = 3

90 = k(3)
90 = 3k
3k/3 = 90/3
k = 30

The constant of proportionality is 30.