Q)Sana light 2 candle for study.Thick candle take 6 hr to melt and thin take 4 hr.Sana slept while studying.how long sana study if at that tym thick candle length is twice the thin candle.

• assume that the total length of candle is x
  thick candly decay per hour =x/6
  thin candle decay per hour= x/4
  so after first hour decay = thick 5x/6 thin 3x/4
  after two hour= thick 2x/3 thin x/2
  after three hours thick = x/2 thin=x/4
  so ans will be = 3 hours
  
• 10 years agoHelpfull: Yes(12) No(1)
• Ans. is 3 hrs
  for thick candle,
  decay in 1 hr=1/6
  decay in 3 hr=3/6=1/2
  length=1/2
  for thin candle,
  decay in 1 hr=1/4
  decay in 3 hr=3/4
  length=1/4
  so, L=2l
  
• 10 years agoHelpfull: Yes(4) No(1)
• assume- initial length=l, thin remains x, thick remains 2x,
  time of study (by thin candle)=time of study (by thick candle)
  (l-x)*4/l=(l-2x)*6/l //time =decay length*rate of decay
  //rate of decay=time/length
  on solving- x=l/4
  so put x=l/4 again in- time of study=(l-x)*4/l
  ans=3
  
  
• 10 years agoHelpfull: Yes(3) No(1)
• 3hrs is the answer
  because in 3 hrs thick candle will be of 1/2 length and thin candle will be 1/4 of the original length
• 10 years agoHelpfull: Yes(1) No(0)
• its a MR question
  just suggest the possible ans
  
• 10 years agoHelpfull: Yes(0) No(2)
• ans is 6 hours
  let us think both the candles are 12m long so after 3hr thin candle left 3m or thick candle left 6m which is twice of thin candle so both candle light for 6hr
  
• 10 years agoHelpfull: Yes(0) No(7)
• for 2 hours
• 10 years agoHelpfull: Yes(0) No(3)
• 2 Hours . Bcoz 6-2 =4 Which is twice to 4-2=2.
• 10 years agoHelpfull: Yes(0) No(3)
• if she needs two candels simunatneously to study then of course answer is 2
  
• 10 years agoHelpfull: Yes(0) No(1)
• Ans -3
  Assume both candle are of length 6 then after first hour remaining height of both the candles are 5 and 4.5 respectively now after 2 hr remaining height of candles are 4 and 3 and after 3 he's remaining height of the candles are 3 and 1.5.
  Now you can apply this for any length of the candles.
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• answer is 3...for sure!
• 10 years agoHelpfull: Yes(0) No(0)
• let us assume height of candle is 12 cm (lcm 4,6)
  initial both candle 12cm
  thick candle=12/2=6hour;(per hour melt)
  thin candle=12/3=4 hour;(per hour melt)
  now,first hour thick candle- 10cm,thin candle=9cm
  second hour thick candle = 8 cm,thin candle=6cm
  third hour thick candle = 6 cm,thin candle=3cm
  condition proved,hence sana slept for 3 hour
  ANS=3 hour
• 10 years agoHelpfull: Yes(0) No(0)
• 2 hours.
  Let's suppose we assume the candles to be separate blocks and each block is of 1 hour, then at the initial stage.
  
  1 candle = 0 0 0 0 0 0
  2 candle = 0 0 0 0
  
  After 1 hour when one of the block is melted in both the candles then,
  
  1 candle = 0 0 0 0 0
  2 candle = 0 0 0
  
  After another 1 hour i.e. total 2 hours, one more block of the candle will melt so:-
  
  1 candle = 0 0 0 0
  2 candle = 0 0
  
  Hence after 2 hours we can say that the thick candle will be twice the length of the thin candle.
• 3 years agoHelpfull: Yes(0) No(0)