GMAT PREP (Average Speed)??

IMO C

Again how did you arrive to your answer....Please help....

Jane walked for 4 miles. What was her average speed for the first 2 miles?

(1) Jane's average speed for the 4 miles was 3.2 miles per hour.
(2) It took Jane 15 minutes longer to walk the second 2 miles than it took her to walk the first 2 miles.

The speed for the first 2 miles?

Statement I

speed =3.2
distance = 4
time=4/3.2
Insufficient, tells us nothing about the first 2 miles or last 2 miles.


Statement II

if time taken for first 2 mile = x
then, time taken for last 2 miles = x+15
we dont know anything about speed, therefore insufficent.

Statement I & II

(4/3.2)*60 = x+x+15

x=12.5

d=2 miles
time = 12.5
speed = 2/12.5 miles/minute

Hence sufficient.

(1) Jane's average speed for the 4 miles was 3.2 miles per hour.

3.2 miles 60 mins
4.0 miles 75 mins

Insuff

(2) It took Jane 15 minutes longer to walk the second 2 miles than it took her to walk the first 2 miles.

first 2 miles can be 30 and next 2 miles 45 - difference 15
again, first 2 miles can be 40 and next 2 miles 55 - difference 15

Both together...
4 miles, 75 mins, 15 minutes longer...

30 for first 2 miles and 45 for next 2... in addition 75

Choose(c).