A person covers half of his journey at 30 km / hr and the remaining half at 20 km / hr. The av

Name: Problem 11, Chapter 15: The Pearson Guide to Objective Arithmetic for Competitive Examinations
Uploaded: 2022-03-06T15:32:35-08:00
Duration: 1 min 46 s
Channel: Saman Zulfiqar
Description: A person covers half of his journey at 30 km / hr and the remaining half at 20 km / hr. The average speed for the whole journey is (a) 25 km / hr (b) 28 km / hr (c) 32 km / hr (d) None of these

step 1 Our question is one car moving on straight road covers one third of a distance with 20 km per ho

Question

A person covers half of his journey at $30 \mathrm{~km} / \mathrm{hr}$ and the remaining half at $20 \mathrm{~km} / \mathrm{hr}$. The average speed for the whole journey is (a) $25 \mathrm{~km} / \mathrm{hr}$ (b) $28 \mathrm{~km} / \mathrm{hr}$ (c) $32 \mathrm{~km} / \mathrm{hr}$ (d) None of these

    A person covers half of his journey at $30 \mathrm{~km} / \mathrm{hr}$ and the remaining half at $20 \mathrm{~km} / \mathrm{hr}$. The average speed for the whole journey is
(a) $25 \mathrm{~km} / \mathrm{hr}$
(b) $28 \mathrm{~km} / \mathrm{hr}$
(c) $32 \mathrm{~km} / \mathrm{hr}$
(d) None of these

The Pearson Guide to Objective Arithmetic for Competitive Examinations

Dinesh Khattar 2nd Edition

Chapter 15, Problem 11

Instant Answer

Solved by Expert Saman Zulfiqar

03/06/2022

Step 1

Since the person covers half of the journey at each speed, the distance covered at each speed is $ \frac{D}{2} $ kilometers. Show more…

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A person covers half of his journey at $30 \mathrm{~km} / \mathrm{hr}$ and the remaining half at $20 \mathrm{~km} / \mathrm{hr}$. The average speed for the whole journey is (a) $25 \mathrm{~km} / \mathrm{hr}$ (b) $28 \mathrm{~km} / \mathrm{hr}$ (c) $32 \mathrm{~km} / \mathrm{hr}$ (d) None of these

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Key Concepts

Time-Distance Relationship

This concept involves understanding that time equals distance divided by speed. By calculating the time for each segment of the journey and summing them, one can determine the total time taken to compute the average speed.

Harmonic Mean

When equal distances are traveled with different speeds, the overall average speed is best calculated using the harmonic mean. This mean is appropriate because it accurately accounts for the inverse relationship between speed and time when distances are constant.

Average Speed

Average speed is the total distance traveled divided by the total time taken. It is an important concept in motion problems and requires careful handling when different segments of the journey are covered at different speeds.

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