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Sunday, August 22, 2010

RGS Primary 2009 PSLE Math Prelim Paper 2 Q17

At 9.30 am, Train A which was 200 m long, pulled out of Nanas Station and travelled towards Dadas Station at a uniform speed of 80 km/h. Half an hour later, Train B which was 150 m long, left Dadas Station and travelled towards Nanas Station at a uniform speed of 90 km/h.

a) How far has Train A travelled when Train B left Dadas Station?
b) The two trains met each other in a tunnel. Both trains took 15 minutes to completely travel through the tunnel. Calculate the length of the tunnel.


Distance = speed x time
= 80 km/h x (1/2) hour
= 40 km

Answer: 40 km

(Train A) distance
= 80 km x (1/4) hr
= 20 km

(Train B) distance
= 90 km x (1/4) hr
= 22.5 km

Length of Tunnel
--> 20km + 22.5km - 0.2km (Train A's length) - 0.15km (Train B's length)
= 42.15 km

Answer: 42.15 km

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