Sunday, October 3, 2010

Speed P6 2010 SA2 Nanyang P2 Q10

Kingsley planned to cycle from Town P to Town Q. If he were to cycle at 10 km/h, he would reach Town Q at 7.45 p.m. If he were to cycle at 12 km/h, he would reach Town Q at 7.15 p.m. What was the distance between Town P and Town Q? [3 marks][Answer given: 30 km]


                                                          1/2 h
 ---> 10 km/h                         7.15 pm            7.45 pm
 |-------------------------------|-----------------|
P                                                                       Q
 -----> 12 km/h                                             7.15 pm

10 x 1/2 = 5 km     Difference in distance

12 - 10 = 2 km/h     Difference in speed

2 km --> 1 h

5 km --> 5/2 x 1 = 2 1/2 h       Total time to cause the difference in distance

12 x 5/2 = 30 km    Note: use 12 km/h (For 10 km/h, the journey is not completed yet

It was 30 km.

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