the amount of time it takes Tom to cover the exact distance that Linda has covered (t)

t*6 = (t+1)*2
6t = 2t + 2
4t = 2
t = 1/2 hrs


the amount of time it takes Tom to cover twice the distance that Linda has covered? T
t*6 = 2(t+1)*2
6t = 4t +4
2t = 4
t = 2 hrs


T-t = 3/2 hrs = 90 mins

Option D

gmatblood wrote:Tom and Linda stand at point A. Linda begins to walk in a straight line away from Tom at a constant rate of 2 miles per hour. One hour later, Tom begins to jog in a straight line in the exact opposite direction at a constant rate of 6 miles per hour. If both Tom and Linda travel indefinitely, what is the positive difference, in minutes, between the amount of time it takes Tom to cover the exact distance that Linda has covered and the amount of time it takes Tom to cover twice the distance that Linda has covered?

60

72

84

90

120

After 1 hour of walking at 2 miles per hour, Linda has traveled r*t = 2*1 = 2 miles.

Every 30 minutes, Linda travels 1 mile, while Tom travels 3 miles (since his rate is 6mph).

Thus, 30 minutes later:
Linda = 2+1 = 3 miles.
Tom = 3 miles.
Same distance traveled by each.

1 hour later:
Linda = 3+1 = 4 miles.
Tom = 3+3 = 6 miles.

1.5 hours later:
Linda = 4+1 = 5 miles.
Tom = 6+3 = 9 miles.

2 hours later:
Linda = 5+1 = 6 miles.
Tom = 9+3 = 12 miles.
Tom has traveled twice the distance that Linda has covered.

2 hours later - 30 minutes later = 90 minutes.

The correct answer is D.