Two trains start at the same time, P from A to B and Q from B to A.If they arrive at B and A,respectively, $$2\frac{1}{2}$$ hours and 10 hours after they passed each other, and the speed of P is 90 km/hr, then the speed of Q in kin/hr is?
Let the distance between A and B be 'd'
speed of Q be q
't' be the time taken for them to meet
d/(90+q) =t
d/(t+10)=q
d/(t+(5/2))=90
d=90t+225
d=90t+qt
d=qt+10q
qt=225
q=9t
$$t^{2}$$=25
t=5 hours
q=9*5=45 km/hr
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