Word problem involving the least common multiple of 2 numbers

They are back  at starting line:

J:          10            20              30          40    minutes

K:     6        12   18      24       30      36    

So they meet again at 30 minutes at the starting line..... I think you can take it from here.......

Justin walks  1/10  of a lap in one  minute

Keiko walks 1/6 of a  lap in one minute

The LCM of 6 and 10  = 30  = the number of  minutes until they meet again at the  starting line

In that time   Justin walks  (1/10) * 30    = 3 laps

And Justin  walks  (1/6)*30   = 5 laps