An aeroplane leaves an airport and flies due north at a speed of 1000 km per hour. At the same tune, another aeroplane leaves the same airport and flies due west at a speed of 1200 km per hour. |How far apart will be the two planes after 1`1/2

Answer

`300sqrt(61) km`

Explanation

Distance covered by first plane in `1(1)/(2)` hours `=OP=1500 km` (norht).
Distance covered by second plane in` 1(1)/(2)` hours `=OQ=1800 km` (west).
Distance between the two planes after `1(1)/(2)` hours. `PQ=sqrt(OP^(2)+OQ^(2))=300 sqrt(161) km`.