EgmatQuantExpert wrote:

Jack and Jill both left their respective homes at 1 PM. Jack walked till a school that was between 2.5 kilometers and 3 kilometers from his home, inclusive, and returned home between 1:55 PM and 2:05 PM. If Jill walked 5 kilometers more than Jack and returned to her home at 3 PM, which of the following statements must be true?

I. The walking speed of Jill was greater than that of Jack

II. Jack’s walking speed was close to 3 kilometers per hour

III. Had Jack covered 0.5 more kilometers every 30 minutes, his walking speed would have been greater than Jill’s

A. I only

B. II only

C. III only

D. I, II and III

E. None of the above

At 1:00PM, Jack walked to school that was between 2.5-3 km from his home, and then returned home between 1:55PM-2:05PM. Hence, Jack walked about 5-6km in between 55min and 1h 05min.

At 1:00PM, Jill walked 5km more than Jack and returned home at 3PM, he walked about 10-11km in 2 hours.

(I) The walking speed of Jill was greater than that of JackWe could set a specific example to eliminate this one.

If Jack walked for 5km in 1 hour, Jill walked for 10km in 2 hours, then the walking speed of them are equal.

If Jack walked for 6km in 1 hour, Jill walked for 11km in 2 hours, then the walking speed of Jack is greater.

Hence this one is wrong.

II. Jack’s walking speed was close to 3 kilometers per hourIt's clear that this one is wrong.

Jack walked about 5-6km in between 55min and 1h 05min. Hence, his walking speed is between 4.6 and 6.5 km per hour, much greater than 3 km per hour.

III. Had Jack covered 0.5 more kilometers every 30 minutes, his walking speed would have been greater than Jill’sThis one is correct.

If Jack covered 0.5 more km every 30 min, Jack will cover 1 more km every 1 hour. Hence, he could walk about 6-7km in between 55min and 65min.

Jill walked about 10-11km in 2 hours, or walked about 5-5.5km in 1 hours.

It's clear that Jack's walking speed is greater than Jill's. In the worst case, Jack could walk 6 km in 65 min, so his walking speed is 5.54km/h, still greater than Jill's.

The answer is C.

_________________

Actual LSAT CR bank by Broall

How to solve quadratic equations - Factor quadratic equations

Factor table with sign: The useful tool to solve polynomial inequalities

Applying AM-GM inequality into finding extreme/absolute value

New Error Log with Timer