Monday, July 04, 2005

Two Candles!

You have 2 candles. Every candle lights for 60 minutes. You have to find the way to measure 45 minutes.

27 comments:

Derick Thomas said...

You can't cut the candle!

Anonymous said...

burn 1 candle from both ends and also burn the 2nd candle from one end.When the flames on both the sides of the 1st candle meet the time will be exactly 30 mins.At that time the 2nd candle would have also burnt for 30 mins and 30 mins of its burning time will remain.At this time burn its other end and when both flames on the 2nd candle meet the time will be 30+15= 45 mins!

tushita

Anonymous said...

A candle burning on it's side burns far quicker than a candle standing up because the wax melts and drips away... nice piece of lateral thinking, but flawed. Assuming the candles are identical, and symmetrical (which the previous answer would have requried anyway)... a better solution would be to use the two candles to find the middle point (line the candles up and mark a point approximately in the middle, then reverse one candle - the real middle is exactly between the two marks.) Repeat the process to find a mark 1/4 of the way up the candle. Then burn the one candle until you get to that mark. You've also saved a candle.

Anonymous said...

But you are assuming that both candles burn at exactly the same rate.

vinod said...
This comment has been removed by the author.
vinod said...

@tushita....great answer...correct !!!
unfortunately m not able to give the correct ans of tcs interview...got rehected :(

Puzzle solver said...

It is a gud question sombody asked me same question in an interview.I thought it was stress test for me ....

kiran said...

cud u pls gv me the answer

Anonymous said...

Peel the wax off one candle until you have only the string. Fold the string in half twice. This is 1/4 the length of the candle. Burn the remaining candle down to the size of the string.

Nalin Vyas said...

@tushita great answer even i had this question in sap...dint answer ..stil waitin for the results :)

orange said...

lite the candle 1 on both sides.. allow it burn for 15sec/15min(count) whatever based on the question in min or sec.. exactly after 15min/sec lite the second candle on both sides which will obviously burns off in 30 min/sec.. so earlier 15 and now 30(includes the remaining burning of candle 1 also) which is total 45.

Anonymous said...

lite the candle 1 first on both ends allow it burn for 15 min/sec (counting is allowed), exactly after 15 lite the candle 2 on both ends.. obviously it will take 30 to burn off.. along with the remaining of candle 1 as well... therefore previous 15 and now 30 is 45.

Anonymous said...

got rejected in EXL.... for this ...
LOL :)))

If got to solve puzzles at JOB, why not became.... a quizz master....

Pity on these organizations... they ask u puzzle, creative sense , blah blah blah... and at the end all u do is copy and paste....

Amik said...

becoz of dis i was rejctd in d 2nd technicl round of HUAWEI....

Amik said...

becoz of dis i was rejctd in d 2nd technicl round of HUAWEI....

Dheeraj Bansal said...

Can anyone explain this puzzle in a simple way. I am not getting it at all.

CK said...

Got rejected in final round of SISL for nt answering it... he said candles wud be of indefinite shape. this ws d only q'n asked and he said he ll come bck on phone LOL

rajeev said...

The same question asked in oracle interview.
The correct answer according to me.
1st candle start burned from both ends and 2nd one burn from one end.It is sure 1st one can burn only 30 minutes.When 1st one finish to burn till that time we measure only 30 minute only right.So When 1st one completely burn at the same time we start burn the 2nd one from other end also.So from now 2nd one can burn only 15 minute. So 30+15=45 minutes.
Please correct me if i m wrong.

divyesh said...

First of al tak 1 candal .. Nd mark it points at L/4.. Means total per hue <25+25+25+25(%) > thn us candal ko dono side flm jalao.. Nd than dono side ki 25per jal jayegi matlv(25+25=50%)jal jayi.. Tab tak time hua 15 mint.. Xctly usi time par dusri candal ko dono side se jalao.. Yane use jalneme puritarha 30 minut hoge.. Yane(15+30=45)ezy.. But ek bat yeh sirf sochneme thik he coz practical krenge to pehle to candl ki flam nikalne ke liye uska wax melt krna padega.. So candal choti hojayegi.. Pehli candal se.. So both r nt sam.. So yeh as puzl ri8 he.. But nt as practicaly..

Anonymous said...

This is a good question but using candles ruins it. Candles are meant to be lit upright from one end. The solution makes the very sketchy assumption that a candle lit on both ends on its side will burn at the same rate. If you ask this question it would be better to use "rope" or "string" instead of candles. It would be a shame to think a candidate got the question wrong when they were smart enough to not make assumptions about how candles burn when used on their side.

Anonymous said...

At constant temprature may b the above theory is right, here v assume the wind is constant and no external force acts.

And interviewers , Hv u framed this question on your own? Or it's a copy and paste question? B honest, so if u r testing creativity, ingenuity of the candidate, where is yours, how right are you to b on the interviewer's chair

Brendan said...

Light candles, set alarm on watch. Read a book until alarm goes off.

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