AAPL wrote:A certain telephone company offers two plans, A and B. Under plan A, the company charges a total of $0.60 for the first 7 minutes of each call and $0.06 per minute thereafter. Under plan B, the company charges $0.08 per minute of each call. What is the duration of a call, in minutes, for which the company charges the same amount under plan A and under plan B?

A. 2
B. 9
C. 15
D. 21
E. 30
OA B.

Let x = the duration of the phone call (in minutes)

Under plan A, the company charges a total of $0.60 for the first 7 minutes of each call and $0.06 per minute thereafter.
So, the TOTAL cost = $0.60 + (x - 7 minutes)($0.06)
= 0.60 + (0.06x - 0.42)
= 0.06x + 0.18

Under plan B, the company charges $0.08 per minute of each call.
So, the TOTAL cost = 0.08x

What is the duration of a call, in minutes, for which the company charges the same amount under plan A and under plan B?
We want: = 0.06x + 0.18 = 0.08x
Subtract 0.06x from both sides to get: 0.18 = 0.02x
Solve: x = 0.18/0.02 = 9 (minutes)

Answer: B

Cheers,
Brent

Hi All,

We're told that a certain telephone company offers two plans, A and B. Under plan A, the company charges a total of $0.60 for the FIRST 7 minutes of each call and $0.06 per minute thereafter. Under plan B, the company charges $0.08 per minute of each call. We're asked for the duration of a call, in minutes, for which the company charges the SAME amount under plan A and under plan B. This question can be solved in a couple of different ways, including by TESTing THE ANSWERS.

Since Plan A charges a fixed amount for the first 7 minutes, while Plan B charges a higher per-minute rate (8 cents vs. 6 cents), and those numbers are all relatively small, it's likely that the correct answer will be relatively small. Let's TEST Answer B first.

Answer B: 9 minutes
Plan A = $0.60 for the first 7 minutes + ($0.06)(2 extra minutes) = $0.60 + $0.12 = $0.72
Plan B = ($0.08)(9 minutes) = $0.72
These two totals are the same, so this must be the answer.

Final Answer: B

GMAT assassins aren't born, they're made,
Rich

AAPL wrote:GMAT Prep

A certain telephone company offers two plans, A and B. Under plan A, the company charges a total of $0.60 for the first 7 minutes of each call and $0.06 per minute thereafter. Under plan B, the company charges $0.08 per minute of each call. What is the duration of a call, in minutes, for which the company charges the same amount under plan A and under plan B?

A. 2
B. 9
C. 15
D. 21
E. 30

OA B.

We can let m = the duration of the call, in minutes, and create the equation:

0.6 + 0.06(m - 7) = 0.08m

0.6 + 0.06m - 0.42 = 0.08m

0.18 = 0.02m

9 = m

Answer: B