Mathematics
posted by Lydia .
For the first 1 1/2 hours of a 91km journey the average speed was 30km/h.If the average speed for the reminder of the journey was 23km/h, calculate the average speed for the entire journey.

Distance travelled for 1.5 hours at 30
= 1.5*30 km
= 45 km
Remainder of journey
= 9145
= 46 km
Time required at 23 km/hr
= 46/23
= 2 hours
Total distance = 91 km
total time = 1.5 + 2 = 3.5 hours
Average speed
= 91/3.5 km/hr
=26 km/hr