Given:
The graph of a proportional relationship.
To find:
The constant of proportionality, the value of y when x is 24 and the value of x when y is 108.
Solution:
If y is directly proportional to x, then
...(i)
Where, k is the constant of proportionality.
The graph of proportional relationship passes through the point (5,15).
Substituting x=5 and y=15 in (i), we get
Therefore, the constant of proportionality is 3.
Substituting k=3 in (i) to get the equation of the proportional relationship.
...(ii)
Substituting x=24 in (ii), we get
Therefore, the value of y is 72 when x is 24.
Substituting y=108 in (ii), we get
Therefore, the value of x is 36 when y is 108.