a bicyclist encounters a series of hills.uphill speed is always v1 and downhill speed is always v2.the total distance travelled is l,with uphill and downhill portions of equal length,the cyclist's average speed is
1.v1/v2
2.v2/v1
3.v1v2/v1+v2
4.2v1v2/v1+v2
Total distance traveled = I
Total distance traveled uphill = Total distance traveled downhill = I/2.