Math question for S3

2010-09-14 7:33 pm

Please to solve the following question:

Cyberwork provides two plans for mobile phone users.

Plan A the basic monthly fee is $128
Free air time 200min
Extra air time rate ($/min) 0.9

Plan B the basic monthly fee is $188
Free air time 350min
Extra air time rate ($/min) 0.7

**Note: Part of 1 min is calculated as 1 min.
Mr White chose plan A last month. He found that the air time he
used was less than 350 minutes but he could have paid less if he
had chosen plan B. At least how many minutes of air time did he
use last month?

回答 (1)

[匿名]

2010-09-14 8:16 pm

✔ 最佳答案

Let x min. be the air time Mr. White used last month. So we compare the fee of plan A and B that give us
Plan A basic$ + extra air time$ > $188 (because he used less than 350min)
i.e. 128+(x-200)0.9 > 188
x >266.67
so the least value of x is 267 (round up to full minutes)
He used at least 267 minutes of air time.

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