Mr. W travelled 370 km, 390 km and 720 km at speeds of 37 km/hr, 5 km/hr and 8 km/hr, respectively. Find his average speed in km/hr.​

Correct option is D

Given:
Mr. W traveled 370 km at a speed of 37 km/h.
Mr. W traveled 390 km at a speed of 5 km/h.
Mr. W traveled 720 km at a speed of 8 km/h.
Formula Used:
​$$\text{Average speed} = \frac{\text{Total distance traveled}}{\text{Total time taken}}$$​​
Solution:
Time for the first part (370 km at 37 km/h) =$$\frac{370}{37} = 10 \, \text{hours}$$​ 

Time for the second part (390 km at 5 km/h) = $$\frac{390}{5} = 78 \, \text{hours}$$​

Time for the third part (720 km at 8 km/h) = $$\frac{720}{8} = 90 \, \text{hours}$$​​
Total distance = 370 + 390 + 720 = 1480 km
Total time taken = 10 + 78 + 90 = 178 hours
Average speed = $$\frac{1480} {178} =8 \frac{28}{89} km/hr$$​​