One hour after Yolanda started walking from X to Y, a distance of 31 miles, Bob started walking along the same road from Y to X. If Yolandaâs walking rate was 1 miles per hour and Bobâs was 2 miles per hour, how many miles had Bob walked when they met?  Choose the correct answer
A) 19	B) 20	C) 22	D) 21	E) 19.5
Let t be the number of hours that Bob had walked when he met Yolanda. Then, when they met, Bob had walked 4t miles and Yolanda had walked (t + 1) miles. These distances must sum to 31 miles, so 2t + (t + 1) = 31, which may be solved for t as follows   2t + (t + 1) = 31   2t + t + 1 = 31   3t = 30   T = 10 (hours)   Therefore, Bob had walked 2t = 2(10) = 20 miles when they met. The best answer is 20.
<result>B</result>
One hour after Yolanda started walking from X to Y, a distance of 31 miles, Bob started walking along the same road from Y to X. If Yolandaâs walking rate was 1 miles per hour and Bobâs was 2 miles per hour, how many miles had Bob walked when they met?