Q: A car travels for 10 minutes at 30km/h and then for 20 minutes at 45 km/h. The average speed for the whole journey is...
A. 40 km/ h
B. 37 1/2 km/h
C. 20 km/ h
D. 35km/h

Thanks.

I believe it's 37and a half.

How could you say that? Can you give me a solution?

The average velocity is found by calculating the total distance traveled and dividng by the total time of the trip. So step 1: calculate how far he travelled in the first phase when going at 30 KPH, using distance = rate times time. Step 2: calculate how far he travelled in the second phase when going 45 KPH. Step 3: add these two distances to get the total distance covered. Step 4: add the time taken in phase 1 to the time in phase 2 to get the total time. Step 5: divide the total distance by the total time to get the avarege velocity.

Hint: the answer that anime36501 gave is incorrect.