Grace's house is 90 meters closer to the fountain. After how long are the boys walking together

Question

Allie's walking rate is 2 meters per second 

Grace's walking rate is 1.5 meters per second 

Answer 1

 

setup is:

 

2x = 90 + 1.5x

 

solve: 

x = 180 secs = 3 min 

Allie caught up with Grace after 3 mins