Naveen travelled a distance by car at 60 km/hr. for 35 minutes. He further travelled by bus at 40 km/hr. for another 35 minutes. Find the average speed for the whole journey.

Distance by car = 60 km/hr × 35/60 hr = 35 km. Distance by bus = 40 km/hr × 35/60 hr = 23.33 km. Total distance = 58.33 km. Total time = 70 min = 7/6 hr. Average speed = Total distance / Total time = 58.33 × 6/7 = 50 km/hr. Alternatively, average speed when distances are equal but speeds different is (2×s1×s2)/(s1+s2) = (2×60×40)/(60+40) = 4800/100 = 48, but this formula applies when TIME is equal, not distance. Since time IS equal (35 min each), we can use harmonic mean: 2/(1/60+1/40) = 2/((2+3)/120) = 240/5 = 48. Wait, let me recalculate: total distance = 35+23.33 = 58.33 km, time = 1.167 hr, speed = 58.33/1.167 = 50 km/hr.