rohit8865 wrote:

chetan2u wrote:

Skywalker18 wrote:

Last month a phone company charged $ 0.07 per minute for the first 300 minutes of calling time and $0.05 per minute for each minute of calling time in excess of the first 300 minutes . For how many minutes of calling time was Bob charged by the phone company last month?

1) Last month the phone company charged Bob $21.00 for his calling time that was charged at $0.07 per minute.

2) Last month the phone company charged Bob $40.00 for his calling time that was charged at $0.05 per minute.

Hi

hsbinfy and

manishpatwal,

ans should not be C or D, it should be B..

the Q tells you..

first 300 = 0.07 per minute

after 300 = 0.05 per minute..

we have to find TOTAL time..

lets see the statements-

1) Last month the phone company charged Bob $21.00 for his calling time that was charged at $0.07 per minute.we do not anything about the minutes beyond 300..

Insuff

2) Last month the phone company charged Bob $40.00 for his calling time that was charged at $0.05 per minuteWe know now how many minutes did he speak in excess of 300 =\(\frac{40}{0.05}= 800\) minutes..

ans = 300+800 = 1100

Suff

B

chetan2ui have little difficulty understanding how B is correct

how do you know $40 was counted over a single phone call

option B states the charge @0.05 for the entire month

so there might be chances he used 2*$20= $40 for entire month

then total may be = 300+ 300+ 800= 1400

Please explain experts !!!!!!!

Hi, The best way to solve this question is to set the appropriate equation.

Here, let X = the total time spent on the phone.

Thus you have the equation:

TOTAL CHARGE = .07(300) + .05(X-300)

--> TOTAL CHARGE = 21 + .05X - 15

Where the $21 derives from the .07 cost per minute. And the .05x - 15 derives from the .05 cost per minute after the 300.

Statement 1Last month the phone company charged Bob $21.00 for his calling time that was charged at $0.07 per minute.

Insufficient because we don't know about the second part of the charge, and additionally, this is information we already know.

Statement 2Last month the phone company charged Bob $40.00 for his calling time that was charged at $0.05 per minute.

Sufficient because this tells us that .05X - 15 = 40. Therefore we can solve for X and get the answer.

B.