Speed P6

Cynthia walked to the library from school and at the same time, Mrs Lee walked to school from the library. If they walked towards each other, they would meet 4 min later. If they walked in the same direction, it would take Cynthia 20 min to catch up with Mrs Lee whose walking speed was 40 m/min. How far was the library from the school? Assume that Mrs Lee's walking speed was constant at all times.

40 x 4 = 160 m

      X     160
C[        ][    ]L

     X + 160
C[              ][                    ]
                 L[                    ]

20 min --> X + 160    Difference in distance

4 min --> X - 160             Difference in distance
20 min --> 5 X - 5 x 160 = 5 X - 800

5 X - 800 --> X + 160
4 X --> 800 + 160 = 960
X --. 960/4 = 240 m

240 + 160 = 400 m

It was 400 m.