A train travels 10 miles at a speed of 50 miles per hour. How fast must the train travel on the return trip if the round-trip travel time is 20 minutes?
- ক) 55 miles/hours
- খ) 60 miles/hours
- গ) 65 miles/hours
- ঘ) 75 miles/hours
উত্তর দেখুন
উত্তর: ঘ) 75 miles/hours
ব্যাখ্যা
D) 75 miles/hour. The outward trip takes 10 ÷ 50 = 1/5 hour, which is 12 minutes. The whole round trip is 20 minutes, so 8 minutes are left for the return. Covering 10 miles in 8/60 hour needs 10 ÷ (8/60) = 75 miles per hour.
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