Bunuel wrote:
megafan wrote:
The cost of a certain phone call was $0.75 for the first 3 minutes and $0.20 for each additional minute after the first 3 minutes. Did the phone call last longer than 15 minutes
(1) The cost of the phone call was less than $4.16
(2) The cost of the phone call was greater than $3.35
While this is a seemingly simple min/max problem, I was wondering if there is a faster way to deal with decimals—as it took me ~4mins to arrive at the solution.
The cost of a certain phone call was $0.75 for the first 3 minutes and $0.20 for each additional minute after the first 3 minutes. Did the phone call last longer than 15 minutesAccording to the above the cost for n minutes, where n>3, is \(75 + (n-3)*20=20n+15\)
cents. W need to find whether n>15. The cost for 15 minutes is \(20n+15=20*15+15=315\) cents, so we need to find whether the cost is greater than 315 cents.
(1) The cost of the phone call was less than $4.16. Not sufficient.
(2) The cost of the phone call was greater than $3.35. Sufficient.
Answer: B.
What is the flaw in my reasoning -
0.75X3 + A X 0.2 = Total Cost.
Where A is the # of Minutes after 3 Minutes.
Basically, now we boil down to if
A>12Statement 1 =
0.75
X3 + A X 0.2 = 4.16
A = 9.55 Minutes - That means A is not greater than 12. Hence with the calculation we did above we can clearly say that this statement is sufficient to forecast that A is not greater than 12.
You should read the stem and the solution more carefully.
1. The cost of a certain phone call was $0.75
2. A in your solution must be more than 15, not more than 12;
3. (1) says that the cost of the phone call was
than $4.16, not equal to $4.16.