RPF 10 Jan 2019 Question 101

Question 101

A Person travels an Equilateral triangular area with the speed of 12kmph, 18kmph, and 36kmph along the planes of the triangular field. Find the average speed of the journey.


Since, the distance travelled is equal on the three sides, hence average speed will be the harmonic mean of the speeds.

= $$\frac{3}{\frac{1}{12}+\frac{1}{18}+\frac{1}{36}}$$

= $$\frac{3}{\frac{3+2+1}{36}}$$

= $$\frac{3}{6}\times36=18$$ km/hr

=> Ans - (D)

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