Question 465935
Get the average speed of the boy in the entire trip by taking the harmonic mean of the rates:

{{{2/(1/10 + 1/9) = 180/19}}} kph.

Multiplying this average rate by 9.5 hr, we get 90 kilometers.  This is the distance traveled in the ROUND TRIP, so to get the one-way distance, divide by 2.
Hence the boy can ride his bike up to 45 km.