Hi APL,

This question can be solved in a couple of different ways; since it makes a direct reference to the AVERAGE SPEED formula, you might find it easiest to just set up that formula and solve:

Total Distance = (Average Speed)(Total Time)

Given the information in the prompt, we have....

(X miles ) = (Average Speed)(Y + 1/4 hours)
Average Speed = (X)/(Y + 1/4)

Final Answer: C

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

AAPL wrote:Suppose a train travels x miles in y hours and 15 minutes. Its average speed in miles per hour is

$$(A)\ \frac{(y+15)}{x}$$
$$(B)\ x(y−\frac{1}{4})$$
$$(C)\ \frac{x}{\left(y+\frac{1}{4}\right)}$$
$$(D)\ \frac{x}{y+15}$$
$$(E)\frac{(y+\frac{1}{4})}{x}$$

The OA is C.

Please, can any expert assist me with this PS question? I don't have it clear. Thanks.

The time, in hours, is y + 15/60 = y + ¼. So, the average rate is x/(y + 1/4) miles per hour.

Answer: C