An aeroplane travels distance 2500 km, 1200 km, and 500 km, at the rate of 500 km/h, 400 km/h and 250 km/h respectively. The average speed of the plane is :

(A) 420 km/h

(B) 410 km/h

• time=distance/speed
  time=2500/500+1200/400+500/250
  5+3+2=10 hrs
  
  speed=total distance/time
  (2500+1200+500)/10
  4200/10=420 km/h(ans)
  
  
  
  
• 12 years agoHelpfull: Yes(4) No(0)
• Total time taken by the aeroplane = (2500/500)+(1200/400)+(500/250) hrs
  =5+3+2 hrs =10 hrs.
  Also total distance travelled = 2500+1200+500 kms
  =4200 kms.
  So, avg. speed = 4200/10 km/hr
  =420 km/hr
• 12 years agoHelpfull: Yes(1) No(1)