Which ball is heavy
Suppose you had 8 billiard balls, and one of them was slightly heavier, but the only way to tell was by putting it on a scale against another. What's the fewest number of times you'd have to use the scale to find the heavier ball?
posted by Foobar @ 1:53 PM
4 Comments:
3 times.
1.Measure 4 Vs 4 balls.
2.From the heavier 4, measure 2 Vs 2
3.
From the heavier 2, measure 1 Vs 1
2 times.
1. Measure 3 vs 3 balls. Leave the other 2 aside.
2. If 3 vs 3 are equal: measure 1 vs 1 from the other 2 to find out the heavier ball.
If one of the sets of 3 is heavier, measure 1 vs 1 from that set of 3 to find out which one's heavier.
Wrong, if you got lucky, you would pick up two balls, one of them being the heavy one by chance, put them both on the scale and notice that one is heavier.
Wrong, if you got lucky, you would pick up two balls, one of them being the heavy one by chance, put them both on the scale and notice that one is heavier.
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