A trip to a destination is made in the following way:

a)550 km by train at an average speed of 55 km/h

b)4500 km by plane at an average speed of 500 km/h

c)400 km by boat at an average speed of 25 km/h

d)55 km by auto at an average speed of 35 km/h

What is the average speed for the entire journey?

Correct option is D

Given:

550 km by train at an average speed of 55 km/h

4500 km by plane at an average speed of 500 km/h

400 km by boat at an average speed of 25 km/h

55 km by auto at an average speed of 35 km/h

Formula Used:

Time =$$\ \frac{Distance}{Speed}$$​​

Solution:

Time taken by train at 55km/hr = $$\frac{550}{55} = 10hrs$$​​

Time taken by plane at 500km/hr =  $$\frac{4500}{500} = 9hrs$$​​

Time taken by boat at 25km/hr =$$\frac{400}{25} = 16hrs$$​​

Time taken by auto at 35km/hr = $$\frac{55}{35} = \frac{11}{7}hrs$$​​

Total distance =550 + 4500 + 400 + 55 = 5505

Total time taken =$$10+9+16+\frac{11}{7} = \frac{70+63+112+11}{7}=\frac{256}{7}\ hrs$$​​

Average speed =$$\frac{5505}{\frac{256}{7}} =\frac{5505 \times7}{256}$$​

​$$=\frac{38,535}{256} = 150\frac{135}{256} \ km/hr$$​​