A boy runs for 20 min at a uniform speed of 20km/he at what speed should he run in next 40 min so that the average speed is 24 km
Answers
Answer:
4 km/h
Explanation:
given that,
A boy runs for 20 min at a uniform speed of 20km/h
20 minutes = 20 × 1/60 h
1/3 hrs
here,
speed = 20 km/h = initial speed
time = 1/3 h
also given
the average speed of the boy = 24 km/h
and time left to cover = 40 minutes
40 minutes = 40/60 h
= 2/3 h
let the final speed of the boy be v
now,
we have,
initial speed(u) = 20 km/h
final speed = v
total time taken = 1/3 + 2/3
= 3/3 = 1 h
average speed = 24 km
we know that,
average speed<v> = (v + u)/t
= final speed + initial speed /total time taken.
putting the values
24 = (v + 20)/1
v + 20 = 24
v = 24 - 20
v = 4 km/h
final velocity = 4 km/h
so,
the boy have to run at the rate of
4 km/h
Answer:
4 km/h
Explanation:
here given,
initial speed(u) = 20 km/h
time taken = 20 minutes
final speed = v
time taken = 40 minutes
so,
total time taken = 20 + 40
= 60 minutes = 1 hour
average speed<v> = 24
<v> = (v + u) /t
24 = (v + 20)/1
24 = v + 20
v = 24 - 20
v = 4 km/h
so,