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[2010]Hyderabad Dream Team CAT & Related BSchools

Ok now!! The dream team is back!
After reasonable success of last year's team, we are back looking for people who can dream and dream big!
The basic structure of team is mentioned below!
11 active players
2 reserves
2 cheerleaders [smiley]
1 manager
People who are eligible...
40 40
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a correction-6 pts excluding A and B. and similarly on BC and CA.

another qsn:
three persons A,B,C start running simultaneously on three concentric circular tracks from three collinear pts P,Q,R resp which are collinear with the centre 'O' and are on same side of the centre:

meaning:
O-centre
P
Q
R
this way.
The speeds of A,B,C are 5,9,8 m/s resp and the lengths of tracks on which A,B,C run are 400m,600m,800m resp.

Q1) If A runs clockwise and C anticlockwise,after how much time will the positions of A,C be collinear with the centre(and on same side),for the fourth time after they start?
a)177 7/9 sec
b)160 sec
c)145 5/11 sec
d)300 sec

Q2) If A runs clockwise and B anticlockwise, after how much time will they be collinear with centre(and on same side) for the first time at their respective starting points P and Q resp.


please post the approach to solve such different radii circular track probs.

Been a long time since I solved some quant stuff...so here I go!
The first thing to do is bring them all to the same level. So imagine that A,B & C all run on the 400 m track. The problem would remain absolutely the same if A runs at 5 m/s, B runs at 6 m/s (he takes 200/3 seconds to complete a trip) and C runs at 4 m/s. Now getting down to solving the stuff,
1) The problem is similar to A & C meeting for the fourth time (now that we've got them to the same level). This happens after 4*400/(4+5) secs. a)

2)B takes 400/6 secs & A 400/5 secs. LCM of these 2 figures tells us when they meet at the starting point. so 400 secs!

Cheers!
Tatimatla
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