PSLE: Dear students, Do not STRESS; Do your BEST; Forget the REST. "You may never know what results come of your action, but if you do nothing there will be no result.” ~ Mahatma Gandhi.


  1. 1000 coins: A dealer has 1000 coins and only 10 money bags. He has to divide the coins over the 10 bags so that he can make any number of coins simply by handing over a few bags. How could he divide the money over the 10 money bags?
  2. The Lock: Suppose you want to send by post a valuable object to a friend. You have a box which is big enough to hold the object. The box has a locking ring which is large enough to have a lock attached and you have several locks with keys. however your friend does not have the key to any lock that you have. You cannot send the key in an unlocked box since it may be stolen or copied. How do you send the valuable object, locked to your friend - so it may be opened by your friend?

2. Send the box with a lock attached and locked. Your friend attaches his or her own lock and sends the box back to you. You remove your lock and send it back to your friend. Your friend may then remove the lock she or he put on and open the box.

1. Put one coin in the first bag, two coins in the second bag, four coins in the third bag, eight coins in the fourth bag, sixteen coins in the fivth bag, thirty two bags in sixth bag, sixty four in seventh bag, one hundred and twenty eight coins in the eigth bag, two hundred and fifty six coins in the ninth bag and he remaining 489 coins in the tenth bag.