M36-94

Question

Fanny and Alexander are  y  miles apart and are traveling in a straight line toward each other at a constant rate of 25 mph and  x  mph respectively. What is the value of  x ?

(1) 1.5 hours before they meet they were 135 miles apart
 
(2)  y = 360  miles

Bunuel · Answer

Official Solution:

Fanny and Alexander are  y  miles apart and are traveling in a straight line toward each other at a constant rate of 25 mph and  x  mph respectively. What is the value of  x ? 
 
(1) 1.5 hours before they meet they were 135 miles apart
 
The combined rate of Fanny and Alexander is  25+x  mph and if 1.5 hours before they meet they were 135 miles apart, then in 1.5 hours together they should cover 135 miles:  (25+x)*1.5=135  (rate*time = distance). We can find  x . Sufficient.
 
(2)  y = 360  miles. Clearly insufficient.

Answer: A

shaliny · Answer

I like the solution - it’s helpful.

doloremvoluptatum · Answer

1.5 hrs ago they were 135km apart now they are y km apart so 135-y is the distance covered in 1.5 hrs and speed is x+25 ..... am I missing sth ?

Bunuel · Answer

Yes, you are missing what “1.5 hours before they meet” means.

At that moment, they have not met yet, so the distance between them is 135. They then meet exactly 1.5 hours later, so the distance between them at the meeting time is 0. That means the distance they cover together during those 1.5 hours is 135, not 135 minus y.

y is the starting distance at some earlier time (when the trip began), but statement (1) is talking about a later snapshot, 1.5 hours before the meeting, and it gives the distance at that snapshot directly. So you use (25 + x) * 1.5 = 135.

doloremvoluptatum · Answer

Yup got it

M36-94

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