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Answer to "A weighty problem"

**First weighing: **

Divide the 27 balls into 3 groups of 9 balls each.

Set one group aside and weigh the other 2 groups against each other (ie one
group in each pan of the scale).

From the way the scale tilts you can determine which of the two groups (of 9
balls each) contains the heavier ball. If the two groups balance then the odd ball
is in the group you set aside.

**Second weighing: **

Take the errant group (of 9 balls) and divide it into 3 groups of 3 balls each.

Again set one group aside and weigh the other 2 groups against each other.

From the way the scale tilts you can determine which of the two groups (of 3
balls each) contains the heavier ball. If the two groups balance then the odd ball
is in the group you set aside.

**Third weighing: **

Take the errant group (of 3 balls) and set one ball aside. Weigh the other
two balls against each other.

From the way the scale tilts you can determine which is the heavier ball.

If the two balls balance then the heavier ball is the one you set aside.

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