Simon walked a total of 32 kilometers by making 16 trips to school.
i.e. to cover 32 km , he is making 16 trip - 32 : 16
So for 1 km, he is making = 16/32 trip
for 1 km , Simon makes 1/2 trip
For, How many trips will Simon have to walk in all to walk a total of 50 kilometers :
Multipliy the 50 km to the trip taken over 1 km : 50 x 1/2 trip
To cover 50 km, the number of trip taken = 25 trips