mandy begins bicycling west at 30 miles per hour at 11:00 A.M. If Liz leaves from the same point 20 minutes later bicycling west at 36 miles per hour, when will she catch mandy?

Answer 1

t = time in hours

rate * time = distance

Wendy's rate is 30 mph

Liz's rate is 36 mph

we want to find out when their travelled distances are the same

Wendy has 20 extra minutes (0.33 hours) in her distance computation

30 * (t + 0.33) = 36t

30t + 10 = 36t

10 = 6t

t = 1.67

t = 1.67 (hour) = 100 minutes.

Answer 2

distance = speed x time = the same distance for both

30X =36(X-1/3), expand, solve for X = Mandy's speed

6X =12

X = 2 hours

Liz' speed = 2-1/3 = 1 hour and 40 minutes