Question

If you bike for 60km at 30km/h and return at 20km/h what is your average speed for the whole trip??

Answer 1

It's all about breaking it down:
If you went 60 km at 30 km/h, how long did it take you to travel that
30*x = 60 Solve for x
Same for the second part
20 *x = 60

So you now know how long the total trip took you. (Add the two x's together)
You also can figure out the total distance (One way is 60 km, so round trip is double that)

To find the average you take
\[Total Distance \div Total time\]