How fast was Jill traveling?

Question

Jack headed north from town at eleven o’clock A.M. at 20 miles per hour. Jill left town 2 hours later traveling south. If they were 500 miles apart at 6 PM, how fast was Jill traveling?

(A) 100 mph

(B) 72 mph

(C) 28 mph

(D) 95 mph

(E) None of these

I got; (B) 72 mph. Is this the correct answer?

Answer 1

Jack travels at 20 mph for 7 hrs.

Distance Jack covers is 140 miles

Distance Jill covers 500-140 = 360 miles

Time taken by Jill to cover the distance = 5 hrs (as she starts at 1pm and travels till 6 pm)

Jills speed = 360/5 = 72mph

Answer 2

Yes, I got 72mph for Jill's speed as well. Nice work!

For reference,I set the equation up in this format:

500 = 7(20) + 5x

Meaning that Jack traveled for 7 hours (11am to 6pm) at 20mph. Therefore, he must have gone 140 miles. Jill is going in the opposite direction, so she traveled 500-140 miles or 360 miles. If she was traveling for 5 hours (1pm to 6pm), she must have been traveling at 72mph to have traveled 360 miles in only 5 hours.