Mind Bender # 4 : Solution

This month’s Mind Bender drew an excellent response — with some 30 of you proposing varying solutions.

Those solutions ranged from …

* Place one bag on the scales at a time, until you discover the lighter one; and
* Put all bags onto the scales, and remove them one at a time for the result; and
* Assuming it is a balancing scale: Put five bags on each side, then remove two at a time to find the lighter bag; through to …
* Simply lift each bag manually to “feel” which bag is lighter, and avoid the need to use the scales at all.

As you’ll recall one of the criteria is that there was to be only ONE weighing. Therefore, by adding, or subtracting bags from the scales, you would actually be making multiple weighings — which is not permitted.

And, unless you work with weights and measures for a living … I’m not sure how accurate a “manual weighing” would prove.

Anyway, there were just four of you who came up with the correct solution for this month’s Mind Bender.

*So, here it is …*

First, you number the bags from 1 to 10.

Then take from each bag a number of coins equal to the number on the bag — one coin from bag No. 1, two from bag No. 2, and so forth.

Weigh them all together – where a total should be 550 grams. However, the result will be light by a number of grams equal to the number of the bag containing the light coins.

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