On a 300-mile trip, a car went 30 miles per hour for the first 100 miles, 50 miles per hour for the second 100 miles, and 60 miles per hour for the third 100 miles. For what fractional part of the time taken for the entire 300-mile trip was the car going 30 miles per hour?

Explanation: প্রথম 100 mile যেতে সময় লাগে \(\frac{100}{30}\) hour. পরের 100 mile যেতে সময় লাগে \(\frac{100}{50}\) hour. শেষ 100 mile যেতে সময় লাগে \(\frac{100}{60}\) hour. Total time taken: \(T = \frac{100}{30} + \frac{100}{50} + \frac{100}{60} = 100(\frac{1}{30} + \frac{1}{50} + \frac{1}{60}) = 100(\frac{10+6+5}{300}) = 100(\frac{21}{300}) = 7\) hours. Time taken at 30 mph: \(t_{30} = \frac{100}{30}\) hours. Fractional part of time: \(\frac{t_{30}}{T} = \frac{\frac{100}{30}}{7} = \frac{100}{210} = \frac{10}{21}\).