Question

A swimmer swims 90m long pool.he covers the distance of 180m by swimming from one end to other end back along the same path.if he covers the first 90m at speed of 2m/s,then how fast he swims so that his average speed is 3m/s?

Answer 1

Hi friend !

Length of the pool = 90m

Speed to cover first 90 m = 2 m/s

Speed = distance / time
Time = distance / speed
Time taken to cover first 90 m = 90 / 2 = 45 sec


Time taken to travel the next 90 m back = t₂

Total distance = 180 m

Total time to cover 180 m = 45 + t₂

Average speed to travel 180 m = 3 m/s

Average speed = Total distance covered / Total time taken

3 m/s = 180 / 45 + t₂

By cross multiplication , we get :

3× [45 +t₂] = 180

45 +t₂ = 180 /3

45 +t₂ = 60

t² = 60 - 45

t² = 15

Hence , time taken to travel back 90 m = 15 sec
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How fast he swim so that his average speed is 3m/s ?
ANS :-
distance = 90 m
time = 15 sec

Speed = distance / time
= 90 / 15
= 6 m/ s

Hence , he must swim with a speed of 6 sec to make his average speed to be 3 m/s

Answer 2

Answer:

Hi friend !

How fast he swim so that his average speed is 3m/s ?

ANS :-

distance = 90 m

time = 15 sec

Speed = distance / time

= 90 / 15

= 6 m/ s

Hence , he must swim with a speed of 6 sec to make his average speed to be 3 m/s

Explanation: