Ans:25 coins Solution: We have 3 bags - so,totally 90 coins 1)First 10 steps - we have 3 bags so,10 steps* 3 bags= 30 coins.That 30 coins from individual one bag and then dispose that bag.Then you have 2 bags only 2) for next 15 steps :15 steps*2 bags= 30 coins,similar like first one ,dispose that bag also.Then,you have only one bag. 3) for next 5 steps: 5steps*1bag= 5 coins Remaining= 25 coins