Puzzle Contest-146

[HELP]

10 matchsticks each in 10 matchboxes. Every matchstick weighs 1 gram except in one matchbox which weighs 2 grams. With just a weighing machine and allowed to weigh only once, how will u pick the odd matchbox out????

[vireshwar]

just start to put 1-1 matchboxes on both sides of weighing machine and watch if both sides are balanced or not, and put again 1-1 matchbox and keep doing it untill u find some imbalance in weighing machine. Then which side goes upward on putting that matchbox that is the required odd matchbox.
am i right.

[aniruddhabasak]

Divide match boxes in groups as 3-3-3-1 or 5-5
For 3-3-3-1 combination:
1. Weigh the groups of 3 match boxes in between them. This will sort out which group has the heavier match box. If not, then the group which has only 1 match box is the odd member.
2. If the group of 3 match boxes has the odd member then divide them into 1-1-1 group & weigh...This will surely sort out the odd member.

For 5-5 combination:
1. Weigh the groups.
2. Heavier group is divided into 2-2-1 combination & keep continue...This will sort out the heavier member

[smileey]

Weigh the following set:
1 match stick frm match box 1, 2 frm box 2, .........10 frm box 10.
Now, frm this weight, we can find which is the odd box

[deesam]

hw can we pick out the odd one using the weighing machine only once..pls explain

[smileey]

If all the boxes were fine,we expect total weight to be 55grams. Now if total weight is 56, it means the match stick from box 1 was 2grams, if total weight is 57, box 2 is abnormal and so on.