Problem Solving

LulaBrazilia wrote:One hour after Yolanda started walking from X to Y, a distance of 45 miles, Bob started walking along the same road from Y to X. If Yolanda's walking rate was 3 miles per hour and Bob's was 4 miles per hour, how many miles had Bob walked when they met?

A. 24
B. 23
C. 22
D. 21
E. 19.5

Original length of GAP between Bob and Yolanda = 45 miles

Yolanda walks for 1 hour at a speed of 3 miles per hour.
So, Yolanda walked 3 miles during that 1 hour.
Current length of GAP between Bob and Yolanda = 42 miles

At this point, Bob starts walking.
In 1 hour, Bob walks 4 miles towards Yolanda, and Yolanda walks 3 miles towards Bob.
So, EVERY HOUR, the gap decreases a total of 7 miles.
In other words, the GAP between Bob and Yolanda SHRINKS at a rate of 7 miles per hour.

Time = distance/rate
So, time = 42/7 = 6 hours
So, it will take 6 hours for the gap to shrink from 42 miles to 0 miles.

Bob walks at a rate of 4 miles per hour.
So, Bob's travel distance = (rate)(time) = (4)(6) = [spoiler]24 miles = A[/spoiler]

Cheers,
Brent