Answers

The Brainliest Answer!
2015-07-09T16:50:38+05:30
For same distance travelled avg speed(<v>) is 
ntimesdistance/<v>=1/v₁+1/v₂+1/v₃..................+1/Vn

Here;
2/<v>=1/30+1/45      ;here 2 bcoz train makes 2 trips 
THEREfore <v>=(2*30*45)/(30+45)
                       =(60*45)/75
                       =36km/hr
2 5 2