Answer:
Here 7.5 is the proportionality constant.
Explanation:
Here, according to the question:
30 songs are played in 4 hours
⇒ 15 songs are played in 2 hours
and 7.5 songs are played in 1 hour.
or, 1 ∝ 7.5
So, here 7.5 is the proportionality constant.