Question 933777
You run back to school at 4.2m/s
distance = 400 m

time taken by you to reach school = 400/4.2= 95.2 seconds

during that time your friend is walking at 1.9 m/s
so he has walked ahead 1.9*95.2=180.9 m

when you are at school he is 400 + 181  = 581 m ahead of you

catch time = catchup distance /catch up rate

581/(4.2-19)

581/2.3= 252.6 sec

so you run 95.2 sec + 252.6 sec

=