A person travels a certain distance in 10 hours, if he covers the first half at a speed of 30 km/hr and second half with the speed of 20 km/hr, then what will be the total distance covered by him?

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RRB NTPC Exam 19 Jan 2021 click here to view all questions

A person travels a certain distance in 10 hours, if he covers the first half at a speed of 30 km/hr and second half with the speed of 20 km/hr, then what will be the total distance covered by him?

A120 km

B160 km

C100 km

D240 km

Akhilesh ? Apr 18 '25 at 11:40

correct answer is: option d (d)[240 km]
Explanation:

Let \( D \) be the total distance. Each half of the distance is \( \frac{D}{2} \) The time taken for the first half is \( \frac{\frac{D}{2}}{30} = \frac{D}{60} \) hours, and for the second half, it's \( \frac{\frac{D}{2}}{20} = \frac{D}{40} \) hours.

Adding these gives the total time:

\[ \frac{D}{60} + \frac{D}{40} = 10 \]

Finding a common denominator (120):

\[ \frac{2D}{120} + \frac{3D}{120} = 10 \]

Combining terms:

\[ \frac{5D}{120} = 10 \]

Simplifying:

\[ \frac{D}{24} = 10 \implies D = 240 \text{ km} \]

Final Answer: \(\boxed{240 \text{ km}}\)

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correct answer is: option d (d)[240 km] Explanation: Let \( D \) be the total distance. Each half of the distance is \( \frac{D}{2} \) The time taken for the first half is \( \frac{\frac{D}{2}}{30} = \frac{D}{60} \) hours, and for the second half, it's \( \frac{\frac{D}{2}}{20} = \frac{D}{40} \) hours. Adding these gives the total time: \[ \frac{D}{60} + \frac{D}{40} = 10 \] Finding a common denominator (120): \[ \frac{2D}{120} + \frac{3D}{120} = 10 \] Combining terms: \[ \frac{5D}{120} = 10 \] Simplifying: \[ \frac{D}{24} = 10 \implies D = 240 \text{ km} \] Final Answer: \(\boxed{240 \text{ km}}\) Akhilesh ? answered Apr 18 '25 at 11:40

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