SOLUTION: A runner takes off at 5 feet per second. 30 seconds later another runner takes off at 7 feet per second. How long will it take for the 2nd runner to catch the first?

Question 633447: A runner takes off at 5 feet per second. 30 seconds later another runner takes off at 7 feet per second. How long will it take for the 2nd runner to catch the first?
Answer by dfrazzetto(283) (Show Source): You can put this solution on YOUR website!
d = v*t
v1 = 5 ft/s
v2 = 7 ft/s
second runner catches the first when their distances are equal
when second runner starts, first runner (v1) has been moving for 30 seconds
V1(t+30) = v2(t)
5(t + 30) = 7t
5t + 150 = 7t
2t = 150
t = 75 second

RELATED QUESTIONS
If one runner that runs at 14.6 feet per second, another runner that runs at 11.3 feet... (answered by stanbon)

AN AIRPLANE AT 19,200 FEET IS DESCENDING AT A RATE OF 40 FEET PER SECOND ANOTHER AIRPLANE (answered by ankor@dixie-net.com)

airplane at 19,200 feet descending at a rate of 40 feet per second. Another airplane... (answered by ikleyn)

a long distance runner started at speed of 8mph. 30 minutes later a second runner start... (answered by josgarithmetic)

A runner starts at the beginning of a runners' path and runs at a rate of 6 miles per... (answered by rfer)

A runner starts at the beginning of a runners� path and runs at a constant rate of 5... (answered by josmiceli)

William is diving off a platform 10 feet above sea level. William dives at a rate of... (answered by Fombitz)

A plane is traveling at 270 feet per second. When the plane takes off, the angle of... (answered by Gogonati)

A long-distance runner started on a course at an average speed of 7 mph. Half an hour... (answered by ikleyn)