distance and time --- JMO V and VI

If I travel at 30 km/hr I reach  my destination at 10 O clock.
If I travel a 20 km/hr I reach my destination at 4 O' Clock.
How far is the destination from my house

JMO STD V VI

Answer:

D/30 = t  ------------- 1

and D/20 = t + 6  ------------------- 2

Substituting 1 in 2, we get

D/20 = D/30 + 6

or, D = 360 km