The quantity of matter in a body regardless of its volume or of any forces acting on it.
Least count of the pulse stopwatch is given by

this means each division of the stopwatch will measure 0.1 s of time
After 3 journeys from one end to other we can see that total time that is measured here is shown by the clock as 52nd division
So here total time is given as
Time = (Number of division) (Least count)
now we will have


Explanation:
Starting position at x = 16m
Ending position at x = -25m
Time of flight = 4s
Unknown:
Distance flown = ?
Displacement = ?
Speed = ?
Velocity = ?
Solution:
To find the distance flown, we should understand that the body is moving on the x - plane;
So distance = 16 + 25 = 41m
Displacement is 41m to the left or -x axis
Speed is the distance divided by the time taken;
Speed =
=
= 10.25m/s
Velocity is 10.25m/s along -x axis