Question

There are 12 students in a playground; 11 weigh exactly the same, but one of them is slightly lighter or heavier. There is a seesaw to determine who is the odd one out. Find out the minimum number of times the seesaw will be used.

Answer 1

The minimum number of times is three. First, weigh four against four. Then, use the remaining weighings to isolate the odd student by mixing suspects with normal-weight students.