Aarav has to reach Delhi which is 799 km away in 19 hours. His starting speed for 7 hours was 85 km/hr. For the next 83 km his speed was 83 km/hr. By what speed he must travel now so as to reach Delhi in decided time of 19 hours?

1. A

   12 km/hr

2. B

   14 km/hr

3. C

   6 km/hr

4. D

   11 km/hr

Appeared in: DSSSB 13 August 2024

Explanation

• The total distance is 799 km and the total time is 19 hours.
• In the first 7 hours, the distance covered is 85 km/hr × 7 hr = 595 km.
• For the next part, the time taken to cover 83 km at 83 km/hr is 83 km / 83 km/hr = 1 hour.
• The total distance covered is 595 km + 83 km = 678 km. The total time elapsed is 7 hr + 1 hr = 8 hours.
• The remaining distance is 799 km - 678 km = 121 km. The remaining time is 19 hr - 8 hr = 11 hours.
• The required speed is Remaining Distance / Remaining Time = 121 km / 11 hours = 11 km/hr.

Why Other Options Were Wrong

• Option A: If the speed is 12 km/hr, the distance covered in the remaining 11 hours would be 12 × 11 = 132 km, which is more than the required 121 km.
• Option B: If the speed is 14 km/hr, the distance covered in the remaining 11 hours would be 14 × 11 = 154 km, which is significantly more than the required 121 km.
• Option C: If the speed is 6 km/hr, the distance covered in the remaining 11 hours would be 6 × 11 = 66 km, which is much less than the required 121 km. This would result in not reaching the destination on time.

Related Visual

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Time, Speed, and Distance as background academic context rather than a clinical decision trigger.
• While this is a general aptitude question, the underlying skill of calculating rates is fundamental in many nursing practices.
• Nurses frequently perform similar calculations for tasks such as determining IV fluid infusion rates (mL/hour), calculating medication dosages over time (e.g., mg/hour), and monitoring patient output (e.g., urine output in mL/hour).
• Accuracy in these calculations is critical for patient safety and effective treatment.

How to Approach the Question

• First, carefully read the problem and identify all the given values: total distance, total time, and the speeds/distances for the initial parts of the journey.
• Break the problem down into segments. Here, the journey has three distinct parts.
• For each segment, use the fundamental formula: Distance = Speed × Time. You may need to rearrange it to find the unknown variable (e.g., Time = Distance / Speed).
• Calculate the total distance covered and total time spent after the first two parts of the journey.
• Subtract the completed distance and time from the total journey's distance and time to find what remains.
• Finally, use the remaining distance and remaining time to calculate the required speed for the last leg of the journey.

Concept Tested & Keywords

• Concept Tested: Time, Speed, and Distance
• Stem keywords: reach Delhi, 799 km, 19 hours, speed, travel
• Lead-in keywords: By what speed

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