GMAT 考满分题库

- 数学PS -
A service provider charges c dollars for the first 50 hours of service used per month and 40 cents for each 30 minutes in excess of 50 hours used during the month.If x is an integer greater than 50,which of the following expressions gives this service provider's charge,in dollars,for a month in which x hours of service were used?
  • Ac+0.40x
  • Bc+0.80x
  • Cc+0.40(x-50)
  • Dc+0.80(x-50)
  • Ec+0.40(2x-50)
正确答案: D

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