陈向东数学书里的阅读题

第四章第3题

The electricity used by the water heater was measured seperately and its cost per kilowatt-hour was one-half the cost per kilowatt-hour of the rest of the electricity used. The cost of the electricity used by the water heater was most nearly what fraction of the total cost of all the electricity used?

A.1/11

B. 1/9

C. 1/8

D. 1/5

E. It cannot be determined from the information given

题目我会算，但是我想问问，我标黑体的one-half，到底是1/2还是1.5倍的意思，one-half与one half，one and half有何不同？

谢谢！