Ask Mar­i­lyn

Los Angeles Times - - PARADE - By Mar­i­lyn vos Sa­vant

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.

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