Atrain left a station at noon, travelling at 40 mph. a second train left at the station at 3 pm traveling at 60 mph. at what time will the second train catch up with the first

both train meet at 9.00 pm

Explanation:  

let t is the time after 1st train start  

we know distance = time * speed

D_1 = 40*t

D_2= 60*(t-3)                ( as second train depart after 3hr gap)  

we know

distance by one train = distance traveled by 2nd train i.e

D_1 = D_2

40*t=60*(t-3)  

40*t = 60*t - 60*3  

20*t = 180

t = 9  

hence both train meet at 9.00 pm

i'm just gonna leave this comment here, so i can get a challange done-

explanation:

iron would move it is magnetic there is a mag field around the current in the wire