Quantitative Aptitude Ques 1628

Question: A motorcycle covers 40 km with a speed of 20 km/h. Find the speed of the motorcycle for the next 40 km journey, so that the average speed of the whole journey will be 30 km/h.

Options:

A) 70 km/h

B) 60 km/h

C) 50 km/h

D) 45 km/h

E) 40 km/h

Show Answer

Answer:

Correct Answer: B

Solution:

  • [b] Let speed of motorcycle for next 40 km journey be $ x,km/h. $ Then, $ 30=\frac{2\times 20\times x}{20+x} $
    $ \Rightarrow $ $ 3,(20+x)=4x $
    $ \Rightarrow $ $ 60+3x=4x $
    $ \Rightarrow $ $ 4x-3x=60 $
    $ \Rightarrow $ $ x=60,km/h $