A boat's speed in still water is 9 kmph and the current is 1.5 kmph. A man rows 105 km away and returns. What is his total travel time_________?
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Answer: D. 24 hours
Explanation
Downstream speed equals the boat speed plus current speed, giving ten point five kilometers per hour. Upstream speed equals the boat speed minus current speed, giving seven point five kilometers per hour. Traveling one hundred five kilometers each way takes ten hours downstream and fourteen hours upstream, totaling twenty four hours. Boat and stream problems account for the speed of water currents aiding downstream travel and hindering upstream travel. Travel time for each leg is calculated by dividing distance by the respective adjusted water speed. Total travel journey time is the sum of the separate downstream and upstream transit durations.
Option A underestimates total travel time by miscalculating the upstream return journey duration. Option B suggests eighteen hours, which fails to match the correct sum of downstream and upstream legs. Option C underestimates the combined transit time required for the round trip journey distance.
- Subject
- Mathematics
- Category
- Mathematics
- Topic
- —
- Difficulty
- medium
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