It costs $4 for the first 1/4 hour to use the laundry machine at the

3 hrs 25 min = 205 min

First 15 min ------> $4
Time left is 190 min...

Now, 60 min costs $ 12
1 min costs $ 12/60
190 min costs $ 12/60*190 => $ 38

So, Total cost will be $38 + $4 => $ 42

Hene answer will be (E) $ 42

For the first 1/4 hour, or 15 minutes, it costs $4. For the remaining 3 hours and 10 minutes, or 3 ⅙ hours, or 19/6 hours, it cost an additional 12 x 19/6 = $38. Therefore, the total cost is 4 + 38 = $42.

Answer: E

Cost for the first 15 minutes = $4
Cost for the next 3 hours 10 minutes = 3*12 + 1/6*12 = 36+2= $38

Total cost = 4+38= $42

IMO E

Posted from my mobile device

E is the answer BUT technically shouldn't the person have to pay for the full hour even though they only used 10 minutes?
If it's pay by hour, and you go over 3 hours..you would have to pay for the full hour.

So even though 4+3(12)+(12*1/6) = 42 makes sense, realistically shouldn't it be:
4+4(12) = 52

The process of elimination works best in this question. As per the constraints mentioned in the first two sentences of the question, we can break down the total time of 3 hours 25 minutes into three batches:

First 15 minutes for which the customer has to pay $4.

Next 3 hours for which the customer has to pay $36.

By now, the bill is already $40 and we still have one batch remaining for the last 10 minutes, which will be charged at $12 per hour. This means that the total cost should be more than $40 and there’s only one answer option like that.

The correct answer option is E.

In a lot of questions on the GMAT, remember, getting to the answer is not the same as solving the question if you know how to leverage the process of elimination.

Hope that helps!
Aravind B T

Solution:

Given that It costs $4 for the first 15 min an hence for the first 15 min we have 4$ as the price

For the rest of the time which is 3hrs 10 min= 190 min it cost 12$ for every 60 min

=> 190 * 12/60 = 38 $

Total cost = 4$ + 38$ =42$ (option e)

Devmitra Sen
GMAT SME

Hello fireagablast,

Technically, $12 per hour is the rate at which the customer is charged for any usage of the laundry more than 15 minutes.
In your own calculation, you multiplied 12 by 3 because the laundry was used for 3 full hours. Going by the same logic, don’t you think you should multiply 12 with 1/6th (10 minutes is 1/6th of an hour)? I think you will agree that you should, right? Because that’s how rates work, isn’t it?

Additionally, we cannot assume that the customer has to pay for the full hour despite being told that he will be charged an hourly rate. It isn't logical.

I hope that answers your question!