Home › RRB NTPC › Quantitative Aptitude › Averages › A man covers half of a journey at $40$ km/hr and…
A man covers half of a journey at $40$ km/hr and the other half at $60$ km/hr. Find his average speed for the whole journey.
A$45$ km/hr
B$48$ km/hr
C$50$ km/hr
D$52$ km/hr
Answer & Solution
Correct answer: B. $48$ km/hr
For equal distances, average speed is the harmonic mean: $\dfrac{2xy}{x+y} = \dfrac{2 \times 40 \times 60}{100} = \dfrac{4800}{100} = 48$ km/hr.
Option C ($50$, the arithmetic mean) applies only when *time* is split equally, not distance.
Related questions
A batsman's average over 16 innings is 36. To raise the average to 38 in the 17th innings,The average of 15 numbers is 12. The first 8 average 11 and the last 8 average 14. The 8thIn a branch, 30 clerks average 60 marks and 20 officers average 70. The average of all 50 The average of 6 numbers is 8. If the number 12 is removed, the average of the remaining 5The class mark of the class interval 10-25 is:The average of 10 numbers is 45. A new number, 100, is added to the set. The new average iThe average of the first 10 natural numbers is:The three measures of central tendency are: