A shopkeeper allows people to buy a cold drink bottle in exchange for five empty bottles. A guy had a party at home and spent 77 cold drink bottles at the party. Now he has 77 empty bottles with him.
How many bottles do you think he can buy in exchange for those 77 empty bottles?
There is a bag which have 21 blue balls and 23 red balls. You also have 22 red balls outside the bag. Randomly remove two balls from the bag. * If they are of different colors, put the blue one back in the bag. * If they are the same colour, take them out and put a red ball back in the bag. Repeat this until only one ball remains in the bag. What is the color of the sole ball left in the bag ?