Answer: 5
Step-by-step explanation:
The constant of proportionality is the value k in the equation y = kx
The equation y = kx is for direct proportions.
Plug in x = 3 and y = 15 to solve for k.
y = kx
15 = k*3
k = 15/3
k = 5
The direct proportion equation is therefore y = 5x
This graphs a straight line through (0,0) and (1,5) and (2,10) and (3,15).
All direct proportion graphs go through the origin.
The constant of proportionality is the slope.