Maverickinsky
Par 100 posts (V.I.P)
You are given eight jelly doughnuts. The doughnuts all weigh the same amount except for one which is heavier. You have a balancing scale at your disposal. What's the minimum number of weighings required for you to pick out the heavy doughnut every time?
Two. Weigh three of the doughnuts against three others and leave the remaining two on the table. If the scales are even, the heavy doughnut is one of the two on the table -- weigh them to find out. If the scales are uneven, take the three doughnuts on the heavy end, weigh one of them against another, and leave the third on the table. If the scales are uneven, you've found the heavy one. If not, the heavy one is the one on the table.
Two. Weigh three of the doughnuts against three others and leave the remaining two on the table. If the scales are even, the heavy doughnut is one of the two on the table -- weigh them to find out. If the scales are uneven, take the three doughnuts on the heavy end, weigh one of them against another, and leave the third on the table. If the scales are uneven, you've found the heavy one. If not, the heavy one is the one on the table.