Monday, August 12, 2013

Simultaneous equation

Two persons A and B  are 27 km apart, setting out at the same time, are together in 9 hours if they walk in the same direction, but in 3 hours if they walk in opposite directions. Find their rate of walking.

Answer:
Let A be walking at x km/hr.
Let B be walking at y km/hr.
relative speed when they are walking in the same direction is (x - y) km/hr.
So, 9(x - y) = 27 --------(1)

or (x - y) = 3      ---------(3)
relative speed when they are walking in the opposite direction is (x + y) km/hr
So, 3(x + y) = 27 --------(2)

or, (x + y) = 9 ----------(4)

Solving (3) and (4), we get x= 6 km/hr and y = 3 km/hr

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