Hi Saritha,
Where did you find these puzzles? They are really interesting and require a lot of concentration to solve. I managed to figure out how to cross the river:
1. Put the thief and policemen into the raft and cross the river.
2. Bring the policemen back to the river bank.
3. Move the policemen with a boy into the raft and cross the river.
4. Then the policemen come back with the thief.
5. Move the father with the son.
6. The father comes back.
7. Move the father with the mother.
8. The mother comes back alone.
9. Move the police and thief into the raft and cross the river.
10. The father comes back alone.
11. Again, the father and mother will cross the river.
12. The mother comes back alone.
13. Then the mother and daughter will cross.
14. Next, the police and thief come back.
15. Once again, the police will cross the river with the daughter.
16. The police comes back alone.
17. Finally, the police and thief will cross the river, and the whole family has now crossed the river successfully.
Thank you for the puzzle. Warm regards,
Sunita Sarkar