<PRE><B>Question 387634</B>


Your answer of 200 km is correct!

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Let x = time it takes for 80km/hr train to get to B
then
x- 1/2 = time it takes for 100km/hr train to get to B

80x = 100(x-1/2)
multiplying both sides by 2:
160x = 100(2x-1)
160x = 200x-100
0 = 40x-100
100 = 40x
100/40 = x
5/2 hours = x

Distance then is:
80(5/2) = 40*5 = 200 km

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