Question

A girl covers 40 km at a speed of 10 km/h by bicycle, 25 km at a speed of 5 km/h on foot a
another 100 km at 50 km/h by bus. Find her average speed for the whole journey.​

Answer 1

Given:-

→Speed with which the girl covers

40km(by bicycle)=10km/h

→Speed with which she covers

25km(on foot)=5km/h

→Speed with which she covers

100km(by bus)=50km/h

To find:-

→Average speed of the girl during the whole journey

Solution:

Let the distances covered by the girl be d1,d2 and d3 and the speeds of the girl be v1,v2 and v3 respectively.

=>Time=Distance/Speed

Now,let the three three times be t1,t2 and t3 respectively.

=>t1=d1/v1

=>t1=40/10

=>t1=4h

=>t2=d2/v2

=>t2=25/5

=>t2=5h

=>t3=d3/v3

=>t3=100/50

=>t3=2h

Now,Average speed:-

=>Total distance covered/Total time taken

=>(d1+d2+d3)/(t1+t2+t3)

=>(40+25+100)/(4+5+2)

=>165/11

=>15km/h

Thus,average speed of the girl for the whole journey is 15km/h.