TWO PERSONS A AND B AGREE TO MEET AT A PLACE BTWEEN 11 TO 12 NOON. THE FIRST ONE TOARRIVE WAITS FOR 20 MIN AND THEN LEAVE. IF THE TIME OF THIR ARRIVAL BE INDEPENDET AND AT RNDOM,THEN THE PROBABILITY THAT A AND B MEET IS
[A]1/3 [B]2/3 [C]4/9 [D]5/9
ANSWER: [A]
AS THE FIRST PERSON TO ARRIVE WAITS FOR 20 MINUTES N(E)=20
TOTAL TIME IS 1 HOUR SO N(S)=60
THE OTHER PERSON HAVE TO ARRIVE IN THAT 20 MINUTES
THEREFORE PROBABILITY=20/60=1/3