Thursday, September 9, 2010

Speed P6 2010 Henry Park P2 Q13

A car left City A for City B at 8 am travelling at an average speed of 60 km/h. One hour later, a bus started its journey from City B for City A. At 11.30 am, the two vehicles were 35 km apart after passing each other earlier. If the car reached City B at 1 pm, at what time would the bus arrive at City A?[4 marks][Answer given: 3 pm]


C
-----> 60 km/h                      1 1/2 h
8 am       3 1/2 h         11.30 am      1 pm
|---------------|-----|------- |-------------|
A                         m                            B
TB?         11.30 am    2 1/2 h           9 am
                          35 km               <-----
                     |-------------|                   B

60 x 1 1/2 = 90 km

90 + 35 = 125 km

125/(2 1/2) = 50 km/h

60 x 5 = 300 km

300/50 = 6 h

            3 h            3 h
    |------------|-------------|
9 am         12 pm          3 pm

It was 3 pm.

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