Hi,
For 1st part (direct method):
1. Choose 5 states.
2. For each state, choose 1 senator.
Alternatively, we could arrive at the same answer value by the complement method:
#ways with no restriction
- #ways with 2 senators each from 2 states and 1 senator from 1 state
- #ways with 2 senators from 1 state and 1 senator each from 3 states.
For 2nd part:
Use answer in 1st part and divide by number of ways without restriction.
Thanks!
Cheers,
Wen Shih
P.S. Answer given for 1st part is doubtful.