FUN WITH MATHEMATICS
BRAIN-TEASERS
PUZZLES & RIDDLES
Cement mortar was being prepared by mixing cement to sand in the ratio of 1:6 by volume. In a cement mortar of 42 units of volume, how much more cement needs to be added to enrich the mortar to the ratio 2:9?
Answer: ______
2 units
In a solution of common salt in water, the ratio of salt to water was 30:70 as per weight. If we evaporate 100 grams of water from one kilogram of this solution, what will be the ratio of the salt to water by weight?
Answer: _______
1:2
Half a swarm of bees went to collect honey from a mustard field. Three fourth of the rest went to a rose garden. The rest ten were still undecided. How many bees were there in all?
Answer: _______
80
Fifteen children are sitting in a circle. They are asked to pass a handkerchief to the child next to the child immediately after them. The game stops once the handkerchief returns to the child it started from. This can be written as follows : 1→3→5→7→9→11→13→15→2→4→6→8
→ 10→12 →14→1. Here, we see that every child gets the handkerchief.
(i) What would happen if the handkerchief were passed to the left leaving two children in between? Would every child get the handkerchief?
(ii) What if we leave three children in between? What do you see? In which cases every child gets the handkerchief and in which cases not?
Try the same game with 16, 17, 18, 19, 20 children. What do you see?
Answer: _______
(i) No, all children would not get it.
(ii) All would get it.
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