AboutRohit Agarwal Expertise I can answer questions related to numbers and logic easily. However I sometimes face problems when solving questions that require a lot of creative thinking. I am not good at puzzles which involve a play with words, so please don't ask me to solve such puzzles for you.
Experience I have read a couple of good books containing puzzles and can now claim to have an "expert" in this field. I have been invited to become a member of Mensa.
Organizations INDIAN INSTITUTE OF TECHNOLOGY, DELHI
Education/Credentials Currently doing Dual Degree (B.Tech M.Tech) in Electrical Engineering Department from INDIAN INSTITUTE OF TECHNOLOGY, DELHI
Awards and Honors Numerous certificates recognizing my ability in Mathematics and Logical Thinking
Question HOW CAN I FIND A DEFECT CUBE IN 12 IDENTICAL (IN LOOKING) CUBE BY ONLY THREE TURN WEIGHING.
Answer Easy. But we have to make an assumption that we know that the defective cube is heavier than the rest.
Divide the 12 cubes into 3 groups, each group containing 4 cubes.
Now, weigh group1 and group2. If group1 is heavier, it has the defective cube. If group2 is heavier, it has the defective cube. If both are equal in weight, group3 has the defective cube.
Now that we know which group has the defective cube, just divide that group into 2 subgroups of 2 cubes each.
Now, weigh these subgroups. If subgroup1 is heavier, it has the defective cube. If subgroup2 is heavier, it has the defective cube.
NOTE: It is not possible for both the subgroups to be equal in weight.
Now that we know which subgroup has the defective cube, we just weigh those two cubes which belong to that subgroup and weigh them. The heavier one is the defective one.
The above mentioned algorithm can be modified to find out the defective cube in case we don't know if the defective cube is heavier or lighter, but that will take one more weighing.
