Question

A train travels first 300 km at an average rate of 30 km per hour and further travels the same distance at an average rate of 60 km per hour then the average speed over the whole distance is

• A. $35kmperhour$
  
• B. $40kmperhour$
• C. $42kmperhour$
• D. $45kmperhour$

Answer 1

The correct option is B $40kmperhour$

If a train covers a certain distance at x kmph and equal distance at y kmph than average speed$=\frac{2xy}{x+y}$

Here x=30 km per hour

y=60 km per hour

$\therefore$Average Speed$=\frac{2\times 60\times 30}{30+60}$

$\Rightarrow \frac{360}{90}=40$km per hour