Question

if a man covers for 4/5 part of a circular track in m minutes at the same rate how many minutes does it take to complete one revolution around the entire trank​

Answer 1

Given :

The distance cover by man in m minutes = $\dfrac{4}{5}$ of circular track

To Find :

The time required to complete one revolution around the entire track​

Solution :

Since total distance of the circular track = circumference of track

i.e   D = 2 π radius

Or,  total distance of the circular track = 2 × π × r unit

Let ,  time required to complete one revolution around the entire track​ = T min

According to question

$\dfrac{4}{5}$ of distance of circular track = $\dfrac{4}{5}$ × 2 × π × r

Applying unitary method

∵   Time taken to cover $\dfrac{8}{5}$ × π × r  unit of circular track distance  = m min

So, Time taken to cover 1 unit of circular track distance  =  $\dfrac{m}{\dfrac{8\pi r}{5} }$min

∴   Time taken to cover  2 × π × r  unit of circular track distance  =  $\dfrac{m}{\dfrac{8\pi r}{5} }$ ×  2 × π × r  min

Or,     T = $\dfrac{5m}{8\pi r }$ ×  2 × π × r  min

i.e      T = $\dfrac{5m}{4}$ min

∴   Time = 1.25 m   minutes

Hence,  Time required to complete one revolution around the entire track​ is 1.25 m   minutes   Answer