Question

Pls help with Question 11. I need to submit it by tmr

Answer 1

Answer: 81.85 km/hr

Converting m/sec into km/hr, 25 m/sec = 90 km/hr

Average =

Time = 50/90  =  5/9 hr

next 120 km at an average speed of 80km/h

=> Time = 120/80  = 3/2  hr

last part of its journey at an average speed of 90km/h in 35 Minutes

time = 35 minutes = 35/60 hr = 7/12 hr

Distance covered = 90 * 7 /12  = 105/2  km

Total Distance = 50 + 120  + 105/2  = 435/2 km

Total time = 5/9 + 3/2 + 7/12   =  ( 20 + 54 + 21) /36  = 95/36

Average speed =   (435/2)/(95 /36)  = 432 * 18  /95 = 81.85 km/hr