Sureka travels 10 km to reach her office. She walks 0.5 km by foot at a speed…
2023
Sureka travels 10 km to reach her office. She walks 0.5 km by foot at a speed of 8 km/hr to catch her chartered bus, which travels at a speed of 40 km/hr for the rest of the distance. What is the time taken by her to reach the office?
Answer: C. 18 min — Total travel time for a multi-speed journey is the sum of the time taken on each uniform-speed leg, where time for a leg equals distance divided by that leg's…
- A.
12 min
- B.
15 min
- C.
18 min
- D.
21 min
Attempted by 10 students.
Show answer & explanation
Correct answer: C
Total travel time for a multi-speed journey is the sum of the time taken on each uniform-speed leg, where time for a leg equals distance divided by that leg's own speed — legs are never combined by adding speeds together or by using one leg's speed for the whole trip.
Total distance = 10 km, split into a foot leg of 0.5 km and a bus leg of 10 minus 0.5 = 9.5 km.
Time on foot = distance divided by speed = 0.5 divided by 8 km/hr = 1/16 hr = 3.75 min.
Time by bus = distance divided by speed = 9.5 divided by 40 km/hr = 19/80 hr = 14.25 min.
Total time = 3.75 min + 14.25 min = 18 min.
Cross-check in hours: 0.5/8 + 9.5/40 = 0.0625 + 0.2375 = 0.3 hr, and 0.3 hr × 60 = 18 min — the two routes to the answer agree.