One train travels 200m from A to B with 70 km/ph. and returns to A with 80kmph, what is the average of their speed?

• the formula for this type of problem,i.e. average speed,
  2*x*y/(x+y), where x and y are the up and down speed.
  so ans for this prob is 2*70*80/(70+80)=74.666kmph
  
• 13 years agoHelpfull: Yes(37) No(0)
• speed= dist/time
  so avg speed=400/(200/70+200/80)
• 13 years agoHelpfull: Yes(3) No(4)
• 2(a*b)/(a+b)
• 13 years agoHelpfull: Yes(3) No(0)
• 2xy/x+y
  2(70*80)/70+80
  5600*2/150
  
• 13 years agoHelpfull: Yes(1) No(0)
• 75
  because average = 70+80/2=75
• 1 year agoHelpfull: Yes(0) No(0)