Question 32102
LET THEIR SPEEDS BE A AND B .
WHEN THEY WALK IN SAME DIRECTION THEIR RELATIVE SPEED IS A-B.
DISTANCE =20 KM.
TIME NEEDED TO MEET=20/(A-B) = 10..OR A-B=20/10=2.........................I
WHEN THEY WALK IN OPPOSITE DIRECTION THEIR RELATIVE SPEED IS A+B
DISTANCE =20 KM.
TIME NEEDED TO MEET=20/(A+B)=2...OR...A+B=20/2=10........................II
EQN.I+EQN.II GIVES 
2A=12...OR...A=6
SO B=10-6=4......