Question

Charu's phone company charges $35$ cents each minutes of use during peak hours and $15$ cents each minute of use during non-peak hours.If charu's phone call, what is the greatest number of minutes charged at peak hours rates?

• A. $7$
• B. $13$
• C. $15$
• D. $17$
• E. $21$

Answer 1

The correct option is D $17$

For half an hour call (30 min) Charu’s comp. charged $790$ cents $(1$

=100 cents)$

$30$ minutes call consists of both peak hour (let assume $xmin$) & non- peak hour (let assume $ymin$). So,

$35x+15y=790$

$x+y=30$ min, so non-peak hour time $y=30-x$ & peak hour time $x=30-y$

We need no of min charged at peak hour rate so

$35x+15(30-x)=790$

$35x+450-15x=790$

$20x=340$

$x=17$

Option D