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 :
Choices:
A) 420 km/h B) 410 km/h C) 430 km/h D) 415 km/h E) 440 km/h
time=distance/speed   time=2500/500+1200/400+500/250   5+3+2= 
<gadget id="calculator">5+3+2</gadget>
<output>10</output>
10 hrs   speed=total distance/time   (2500+1200+500)/10   4200/10= 
<gadget id="calculator">4200/10</gadget>
<output>420</output>
420 km/h   420 km/hNSWER:420 km/h
<result>A</result>
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 :