Question

Suppose a bus covers a distance at 40 kmp/h and an equal distance at 60 kmp/h. Then what is the average speed during the whole journey ?

• A. 55
• B. 45
• C. 48
• D. 50

Answer 1

Answer:

C. 48

To find the average speed of a journey where two equal distances are covered at different speeds, use the harmonic mean formula:

$\text{Average Speed} = \frac{2xy}{x + y}$

Where:

• $x$ = speed for the first half = 40 km/h

• $y$ = speed for the second half = 60 km/h

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1. Substitute the values into the formula:
   $\text{Average Speed} = \frac{2 \times 40 \times 60}{40 + 60}$

2. Multiply the numbers in the numerator:
   $2 \times 40 \times 60 = 4800$

3. Add the numbers in the denominator:
   $40 + 60 = 100$

4. Divide the numerator by the denominator:
   $\text{Average Speed} = \frac{4800}{100} = \mathbf{48\text{ km/h}}$

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Final Answer

The average speed during the whole journey is 48 km/h.