A plane left 30 minutes late than its scheduled time and in order to reach the destination 1500 km away in time, it had to increase the speed by 250 km/h from the usual speed. Find its usual speed.

• 1500/x = [1500 / (x+250)] + 1/2...
  
  ...
  
  Then x= 750 kmph
• 15 years agoHelpfull: Yes(12) No(9)
• usual speed is 750 km/hr.
  
  increased speed = 1000km/hr
• 15 years agoHelpfull: Yes(7) No(4)
• usual speed = x
  
  increased speed = x +250
  
  distance =2500
  
  30 minutes late =30/60 = 1/2
  
  so
  
  1500/x -1500/(x+250)=1/2
  
  .
  .
  .
  
  x^2 + 250x-750000 =0
  
  x^2 + 1000x - 750x -750000 = 0
  .
  .
  .
  x=-1000 or x =750 (neglect -sign)
  
  usual speed = 750
  
  increased speed = x +250=1000
  
• 10 years agoHelpfull: Yes(3) No(1)