If the cost of a long-distance phone call is c cen

未知题型

If the cost of a long-distance phone call is c cents for the first minute and 2/3 c cents for each additional minute, what is the cost, in cents, of a 10-minute call of this type?
A.5/3 c
B.6c
C.20/3 c
D.7c
E.23/3 c

A.5/3
B.6c
C.20/3
C.7c
E.23/3

【参考答案】

D
解析：若长途电话费为第一分钟收c美分，以后每增加一分钟，加收2/3 c美分，那么按这种计费方式打10分钟的电......

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