Answer:
r=0.2
Explanation:
Given the quantities x and y
When x=8, y=1.6
On Substitution into y=rx
1.6=8r
r=1.6/8=0.2
When x=15, y=3
On Substitution into y=rx
3=15r
r=3/15=0.2
When x=2, y=0.4
On Substitution into y=rx
0.4=2r
r=0.4/2=0.2
Therefore, the constant of proportionality, r=0.2
NOTE: One set of values is enough to determine this. Others are done for verification.