Time and Distance

speed = \frac{distance}{time}

X km/hour = x  * \frac{1000 metres}{60×60 second}  =   x*\frac{5}{18}  m/sec

If the ratio of the speed of A & B is a:b then the ratio of time taken by them to cover the same distance is \frac{1}{a} :\frac{1}{b} = b:a
“The time taken for covering a certain distance is increasingly proportional to the speed.”
Similarly time taken to finish a work is the inversed proportional to the number of working unit
When by A, cover a certain distance at x km/h & b cover the same distance at y km/h than the average speed of both during the whole journey
journey = (\frac{2xy}{(x+y)})km/h

Difference distance by two moving body in same direction with ‘u’ m/s and ‘v’ m/s
u>v then their relatives speed = (u-v) m/s
u>v in opposite direction they cross to each other = \frac{(a+b)}{(u+v)} second
(With length of a & b meter)
u>v in same direction cross to each other = \frac{(a+b)}{(u-v)} second
if two bodies start at the same time from station A & b to words each other . they have taken time a & b second to reaching A to B & B to A .
then A’s speed: √b:√a