Speed, Time and Distance /
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Q46
2022,
Speed, Time and Distance
A man started from home at 14:30 hours and drove to village, arriving there when the village clock indicated 15:15 hours. After staying for 25 minutes, he drove back by a different route of length 1.25 times the first route at a rate twice as fast reaching home at 16:00 hours. As compared to the clock at home, the village clock is
1. Correct Answer: Option D: 5 minutes fast 2. Explanation: Let's break down the problem step by step: ● Step 1: Calculate the time taken to travel to the village.
○ The man left home at 14:30 and arrived at the village at 15:15 according to the village clock. ○ Therefore, the travel time according to the village clock is 45 minutes. ● Step 2: Calculate the time taken for the return journey.
○ The man stayed in the village for 25 minutes, so he left the village at 15:15 + 25 minutes = 15:40 according to the village clock. ○ He arrived back home at 16:00 according to his home clock. ○ Therefore, the return journey took 20 minutes according to the home clock. ● Step 3: Analyze the speed and distance relationship.
○ The return route is 1.25 times longer than the route to the village. ○ However, he traveled back at twice the speed. ○ If the original route is of distance \(d\) and speed \(s\), then the time taken to travel to the village is \( \frac{d}{s} \). ○ The return route is \(1.25d\) and the speed is \(2s\), so the time taken for the return journey is \( \frac{1.25d}{2s} = \frac{1.25}{2} \times \frac{d}{s} = 0.625 \times \frac{d}{s} \). ● Step 4: Compare the time ratios.
○ The time taken to travel to the village is 45 minutes according to the village clock. ○ The time taken to return is 20 minutes according to the home clock. ○ The ratio of the return time to the travel time should be 0.625 (as calculated from the speed and distance relationship). ○ However, the actual ratio is \( \frac{20}{45} = \frac{4}{9} \approx 0.444 \). ● Step 5: Determine the discrepancy.
○ The discrepancy in the ratio indicates that the village clock is fast. ○ To find out how fast, calculate the expected travel time for the return journey if the village clock were correct. ○ If the village clock were correct, the return journey should have taken \(0.625 \times 45 = 28.125\) minutes. ○ The actual return journey took 20 minutes according to the home clock. ○ Therefore, the village clock is \(28.125 - 20 = 8.125\) minutes fast. ● Conclusion: Since the options provided are in whole minutes, the closest option is that the village clock is 5 minutes fast.
Therefore, the correct answer is Option D: 5 minutes fast.