Bloomberg LP Interview Question for Financial Software Developers






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Two ropes A and B

Ignite both ends of rope A and one end of rope B simultaneously
Rope A will burn out completely in 30 minutes ( refer to reason below if needed ).
Now, at this point ignite the other end of rope B. It will be another
15 mins before the rope B burns out completely. So, it is 30+15=45 mins
for the rope B to completely burn out. thus we can time 45 mins


Reason :

Let L feet be the rope length.
It takes Y mins to burn X feet of the rope, so it takes ( 60 -Y ) mins
to burn the remaining ( L - X ) feet. If you burn both the ends simultaneously,
when the rope burns out, Y=60-Y, so Y has to be 30 mins.

Similarly, it is 15 mins for rope B

- Thirumalai Thathachary December 15, 2009 | Flag Reply
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brilliant

- henry January 20, 2010 | Flag
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Correct solution

- Anonymous December 16, 2009 | Flag Reply
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do they still ask such stupid questions?

- Anonymous December 16, 2009 | Flag Reply
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hahahaha

- Anonymous December 29, 2009 | Flag Reply
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The rope does not burn uniformly. This means that rope B calculation may not be appropriate to calculate 15 min.

- Anonymous January 07, 2010 | Flag Reply
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true! how can you be so sure that ROPE B will be burnt in 15 mins? It is not uniform dude...

- Anonymous January 17, 2010 | Flag
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no, the solution is correct. accepted that the rope does not burn uniformly in length, but it does burn out in 60 mins. so in 30 mins, rope B would have burnt 30mins worth and would have 30 mins worth length left. so by igniting the other end of B when A has burned out would time the remaining 15mins.

- nebu January 18, 2010 | Flag
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That is a perfect explanation!

- Anonymous October 26, 2010 | Flag
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No. The solution is correct. It does not matter whether 1/4 of the rope is burnt in length. We know that exactly 30 minutes of it have burned off. There are 30 minutes of burn time remaining. If we light the other end, it burns twice as fast. Then there are 15 minutes of burn time remaining.

- Anonymous February 09, 2010 | Flag Reply
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Abe Chutiye,
Its not possible,
See, the rope is not uniform.
It wont burn in 15 minutes accuratesly.
U r doing the question as if the rope is uniform.

- Prasad June 18, 2010 | Flag
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0
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HA HA HA Nice Comment :P Ladka Heera Hai !

- Anonymous January 23, 2011 | Flag
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@Anonymous on January 23, 2011

ladkaa heraa hai
toh tu kyaa hilaa rahaa hai ?

- Anonymous May 28, 2012 | Flag
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How about,

Burn rope A in the middle and at the ends. This will take 15 minutes. When that's done, burn rope B from both ends. This will take 30 minutes.

15 + 30 = 45

- Anonymous September 15, 2010 | Flag Reply
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guy... rope is uneven for every part of it... so you cant say that which part will burn in how many minutes... lets say 1/4 of a part A burns in 45 minutes and the rest in 15 minutes ..then??

Anybody still knows the answer ???

- suraj May 06, 2013 | Flag Reply
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here's the correct answer:

1) burn rope A from both the ends and one end of rope B simultaneously ..rope A will burn out in 30 minutes..
2) when rope A burns out , now rope B has 30 more minutes left to burn out.
3)Lit the other end of rope B at that instant...so rope B will take another only 15 minutes instead of 30 to burn out ....therefore 30+15 =45 :) :) :)'

- suraj May 06, 2013 | Flag Reply
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if we fold the rope once and then lit both ends. will it take 15 minutes to burn completely??

- Anonymous June 03, 2014 | Flag Reply


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