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>12

Statement 1 =

0.75X3 + 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.

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