Practicing Success
The average speed of a train running at a speed of 30 km/h during the first 100 km, at the speed of 40 km/h during the second 100 km and at the speed of 50 km/h during the last 100 km is nearly ________. |
40.2 km/h 38.3 km/h 39.2 km/h 37.5 km/h |
38.3 km/h |
Average Speed = \(\frac{Total \;Distance}{Total \;Time}\) Distance = Speed × Time Time= \(\frac{Distance}{Speed}\) T1 = \(\frac{100}{30}\) = \(\frac{10}{3}\) hours T2 = \(\frac{100}{40}\) = \(\frac{5}{2}\) = 2 .5 hours T3 = \(\frac{100}{50}\) = 2 hours Total distance = 100 + 100 + 100 = 300 km Total time = \(\frac{10}{3}\) + 2.5 + 2 = \(\frac{10 + 7.5 + 6}{3}\) = \(\frac{23.5}{3}\) Average speed = \(\frac{300 × 3 }{23.5}\) = 38.29 km/h = 38.3 km/h ( approx) So , Average speed is 38.3 km/h |