Say you have three sacks. Two contain gold coins. The third contains fake coins. Each real coin weighs one ounce. The fakes weigh 1.1 ounces. You have a digital scale. With one weighing, howcan you tell which sack has the fake coins?
—Stan Dec, Ellwood City, Pa.
Want to puzzle this one through on your own, readers? If so, stop here. The answer appears in the next paragraph.
Label the sacks 1, 2, and 3. Put one coin from sack 1 and two coins from sack 2 on the scale. If the weight is 3.1 ounces, sack 1 has the fake coins. If the weight is 3.2 ounces, sack 2 has the fakes. If the weight is 3 ounces, sack 3 contains the fakes.