Le Matou matheux: Proportion

Two puzzles

Two brothers go to the same school. Thay both walk at a constant speed. The oldest one takes ten minutes less to get to school. The youngest brother leaves the house five minutes before the older one.
Where does the oldest brother catch up ?

To go from Paris to Deauille, a motorist travels for half the time at 120 km/h, and for rest of the time at 80 km/h. What is his mean speed on the journey ?

On the return journey, the same motorist travels at 120 km/h until he is halfway there, and 80 km/h for the remaining kilometres. What is his mean speed on the journey ?

document.write('<a href='+url+'><img border="0" src='+image+' /> '+titre+' </a>')

Two puzzles