Question

an athelete runs along a track and covers half the distance with a speed of 20m/s and rest with 30m/s. find his average speed.​

Answer 1

Answer:

Average speed = 24 m/s

Explanation:

let the total distance covered by the athlete be d

so,

half distance travelled = d/2

speed for d/2 = 20 m/s

so,

time taken = (d/2)/20

= d/40

now,

d/2 at the speed of 30 m/s

so,

here,

time taken = (d/2)/30

= d/60

so,

total time taken to cover d

= d/40 + d/60

= (3d + 2d)/120

5d/120

= d/24

now,

Average speed =

total distance travelled/total time taken

= d/(d/24)

24d/d

= 24 m/s

so,

Average speed of the athlete

= 24 m/s

Answer 2

Answer:

Average speed of the athlete = 24 m/s

Explanation:

Given that,

An athelete runs along a track and covers half the distance with a speed of 20m/s and rest with 30m/s

let the total distance covered by the athlete be d

half distance travelled = d/2

so,

speed for d/2 distance 20 m/s

so,

here,

time taken =

(d/2)/20

= d/40

so,

time taken to cover d/2 at a speed of 20 m/s = d/40 s

now,

he covered d/2 at the speed of 30 km/h

so,

here,

time taken = (d/2)/30

= d/60

so,

total time taken to cover d

= d/40 + d/60

= (3d + 2d)/120

5d/120

= d/24

now,

Average speed =

total distance travelled/total time taken

= d/(d/24)

24d/d

= 24 m/s

so,

Average speed of the athlete

= 24 m/s