Save half of the coal
A smart housewife was told that there was a kind of stove which would only consume half of the coal she was burning. She was very excited, and said: "That'll be terrific! Since one stove can save half of the coal, if I buy two, no coal will be needed!" 一位精明的家庭主妇听人说有一种炉子用起来可以比她现在用的'炉子省一半的煤。她听了大为兴奋，说：“那太好了!一个炉子可以省一半的煤，那么如果我买两个炉子的话，不就可以把煤全都省下来了吗?”