Multiple choice general knowledge math & puzzles

There are two candles of equal lengths and of different thickness. The thicker one lasts of six hours. The thinner 2 hours less than the thicker one. Ramesh lights the two candles at the same time. When he went to bed he saw the thicker one is twice the length of the thinner one. How long ago did Ramesh light the two candles

  1. 3 hour

  2. 4 hour

  3. 5 hour

  4. none
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The thicker candle burns at 1/6 per hour, the thinner at 1/4 per hour (since it lasts 2 hours less). Let t be the burning time. Remaining: thicker = 1 - t/6, thinner = 1 - t/4. When thicker is twice thinner: 1 - t/6 = 2(1 - t/4). Solving: 1 - t/6 = 2 - t/2, giving t/2 - t/6 = 1, so t/3 = 1, meaning t = 3 hours.

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