Next door lives a man with his son. They both work in the samefactory.I watch them going to work through my window. The father leavesfor work 10 min earlier than his son. One day I asked him about it andhe told me he takes 30 min to walk to his factory ,whereas his son isable to cover the distance in only 20 min. I wondered if the father were to leave the house 5 min earlier than his son, how soon would the son catch up with the father?
Next door lives a man with his son. They both work in the samefactory.I watch them going to work through my window. The father leavesfor work 10 min earlier than his son. One day I asked him about it andhe told me he takes 30 min to walk to his factory ,whereas his son isable to cover the distance in only 20 min. I wondered if the father were to leave the house 5 min earlier than his son, how soon would the son catch up with the father?
The correct option is B 8.3 mins
Let speed of son be s,and speed of father be f,then
(inverse ratio of the time) ( If D is the distance ,then 
and 
which implies
)
Let speed of dad be 20 and son be 30m/s
Now in 5 mins, the father covers 100 m
And son covers 150 m
The son covers 100 m in 3.33 min,
Hence the son will be able to catch up with the father after 8.3 mins from the start. Option (b).
Let speed of son be s,and speed of father be f,then
(inverse ratio of the time) ( If D is the distance ,then and which implies)
Let speed of dad be 20 and son be 30m/s
Now in 5 mins, the father covers 100 m
And son covers 150 m
The son covers 100 m in 3.33 min,
Hence the son will be able to catch up with the father after 8.3 mins from the start. Option (b).
