Candle light to measure time?

Question

You are given two candles of equal size, which can burn 1 hour each. You have to measure 90 minutes with these candles. (There is no scale or clock). Also u r given a lighter.

Repeat problem to measure 45 minutes.

U CANNOT CUT THE CANDLES!!

Answer 1

You know, thinking about it for two seconds would have been much easier than spending fifteen seconds typing it....

Answer 2

I will assume the candles to be homogeneous, cylindrical and identical. None of the data that you have provided proves otherwise. To solve the problem I would first designate one candle to be "Candle A" and the other to be "Candle B". I would locate the middle of candle A by balancing it on a knife edge. By whatever means available, I would mark the middle of this candle. I would then ignite candle A and when it had burned to the middle mark 30 minutes would have elapsed and I would immediately ignite candle B. When candle B had burned out, 90 minutes would have elapsed since first lighting candle A.

As for determining 45 minutes using the same materials, I would locate the middle of candle A by the same means as before. Then I would take a piece of paper, string, etc and cut a piece to exactly match the length of half of candle A. Next, I would fold the string or paper in half which would give you a length equal to 1/4 the length of the whole candle. I would use the folded string to measure up 1/4 the length of the candle from the bottom of the candle and mark this spot by whatever means available. Then you have only to ignite the candle and let it burn to the mark and 45 minutes will have elapsed.

Both of these solutions are pragmatic and fall within the conditions specified.

Answer 3

Here is the exact way to do it without a tape measure or ruler: (exact = not estimating what is "halfway"):

90 minutes:
Burn one candle completely, then immediately light the other one at both ends. When it's done burning, 90 minutes will have elapsed.

45 minutes:
Start by lighting one candle from both ends and the other from one end at the same time. Immediately when the one you lit from both ends burns out, light the remaining candle from the other end.

Answer 4

For 90 min:
Burn one candle normally for 1 hour.
After the first candle finishes, burn the second one from both ends at the same time for 30 minutes.

For 45 min:
Burn both candle, one normally and other from both ends at the same time for 30 minutes.
After one of the candle finishes, burn the other end of the candle that lit normally for 15 minutes.

Answer 5

(A) break 1 candle into two equal parts
(B) break one part from (A) into 2 equal parts

90 minnutes burn one complete candle + one half
45 minutes burn the 1/4 part from(B)

anything else you want to know ?

Now I have a question for you :

take the 1/4 candle from(B)
(C) split it into 2 equals parts
(D) take one part from (C) split it into 2 equal parts

repeat D until no parts are left

burn all the pieces of candle one by one

Question How long doest it take to burn all the parts ?

Answer 6

burn one candle normally for 1 hour
then burn the second one from both ends at the same time, for 30 minutes

Answer 7

45 Minutes
Burn one candle half way then light it from the other side too.

Answer 8

burn one ( = 60 min ) the light the other from both ends as soon as the first is done ( = 30 min ) that gives 90 min.