Find the Lightest Coin

Computer Science Level 1

True or False?

Chris has 4 coins of distinct weights, of which he wants to find the lightest, using a beam balance with two pans.

He can find it, using the balance 3 times.

True False

Agnishom Chattopadhyay by Agnishom Chattopadhyay , 22, India

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2 solutions

Hasmik Garyaka
Oct 7, 2017

By induction: find the lightest from n in n-1 step. For n=2 obvious. If we found the lightest in n-1, balance it with the nth - 1 more step.

1 Helpful 1 Interesting 0 Brilliant 0 Confused
Katie P
Apr 3, 2021

Picture the balance in your mind: you place two of the weights upon it, find one is heavier, and take it off- that was the first time. Repeating this step two more times, we have gone through each weight and used the balance three times.

0 Helpful 0 Interesting 0 Brilliant 0 Confused

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