Solution: The first caller who win both a music player and concert tickets is 35th caller.
Explanation:
It is given that every 5th caller will win a music player and every 7th caller will win music player.
The caller will win both a music player and concert tickets if he lies in group of every 5th caller as well as every 7th caller.
To find the first caller who will win both a music player and concert tickets, we find the L.C.M. of 5 and 7 .
We know that L.C.M. of 5 and 7 is \(5\times7=35\).
Therefore, the first caller who win both a music player and concert tickets is 35th caller.
