A car covers 15 km, 20 km, 30 km and 12 km at speeds of 20 km/h, 30 km/h, 40 km/h and 30 km/h, respectively. The average speed of the car for the total journey is :
Answer & explanation
Correct answer: option 4
Time = \(\frac{Distance }{Speed}\)
Total time taken = \(\frac{15 }{20}\) + \(\frac{20 }{30}\) + \(\frac{30 }{40}\) + \(\frac{12 }{30}\)
= \(\frac{3 }{4}\) + \(\frac{2 }{3}\) + \(\frac{3}{4}\) + \(\frac{2 }{5}\)
= \(\frac{45 + 40+ 45 + 24 }{60}\)
= \(\frac{ 154}{60}\)
Average Speed = \(\frac{Total Distance }{Total Time }\)
= \(\frac{ 77 × 60 }{154 }\)
= 30 km/h