Assume t=30 seconds.
Let the height of the candle be 300 unit.
Candle A which burns in 30 seconds, burns at a rate of 10 units/second.
Similarly Candle B which burns in 2t(60) seconds, burns at a rate of 5 units/second
Now evaluating the answer choices,
Option A(\(\frac{t}{3}\)) gives time of burning at 10 seconds
In 10 seconds, Candle A burns 100 units making the height of the candle 200 units.
Candle B burns 50 units, making the height 250 units.
Candle B's height is not equal to twice Candle A's height.
Option B(\(\frac{2t}{3}\)) gives time of burning at 20 seconds
In 10 seconds, Candle A burns 200 units making the height of the candle 100 units.
Candle B burns 100 units, making the height 200 units.
Candle B's height is equal to twice Candle A's height. That is our answer!
(Option B)
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