Question 33850
Two planes leave and airport at 10:00am. If the northbound plane flies at 280mph and the southbound plane flies at 320 mph, at what time will they be 1,000 miles apart?

THEY ARE GOING IN OPPOSITE DIRECTIONS.
HENCE THIR RELATIVE SPEED =SUM OF THEIR SPEEDS...THAT IS IF PLANE 1 GOES NORTH 280 MILES IN 1 HOUR ,DURING THE SAME TIME IF PLANE 2 GOES SOUTH 320 MILES.SO IN 1 HOUR THEIR DISTANCE OF SEPERATION =280+320=600
SO D=1000 MILES AS REQUIRED.
SO TIME =DISTANCE /RELATIVE SPEED=1000/600=5/3 HRS=1.67 HRS.