There are nine silver coins marked 1, 2, 3, 4, 5, 6, 7, 8, and 9.
They are supposed to weigh the number of grams that is written on them.
One of the coins is fake and is lighter than it should be.
Find the fake coin using the balance scale twice.
(In reply to Two preplanned weighings
by Brian Smith)
If 1+3+7 is weighted against 2+5+6, the 2+5+6 is sure to go down (be heavy) as its total supposed weight is 13, as opposed to 1+3+7's total of 11, even if one of 2,5,6 is the light coin by 1 or close to 2 grams.
The good coins are not of equal weight, but agree with their markings.
Posted by Charlie
on 2016-01-19 07:56:20