Question

a man walks at the speed of 6km/hr for 1 hour and 8km/hr for the next 1km.what is his average speed for the walk of 2km

Answer 1

Case 1 

Speed = 6km/h 

distance  = 1 km 

Time = distance / speed = 1/6 h 

case 2 

Speed = 8 km/h 

Distance = 1 km 

Time = distance / speed = 1/8  h 

Average speed = Total distance / total time taken 

                         = 1 + 1 / 1/6 + 1/8 

                         = 2 / (4 + 3) /24

                         = 2 / (7/24) = 2 x 24 / 7 = 48/7 = 6.85 km/h

Answer 2

hi there ,

( 1 ) speed = 6 km / hr , distance = 1 km

we know ,

speed = distance / time taken

implies ,

time taken = distance / speed

time taken = 1 / 6 hrs ---------- ( 1 )

secondly ,

in smillar way , for second case

time taken = 1 / 8 hrs ------------(2)

we know average speed = total distance / total time taken

implies

average speed = 2 /( 1 /6 + 1/8)

average speed = 48 / 7 = 6.8km/hr

____________________________________