Mo2men wrote:Each candle in a particular box is either round or square and either scented or unscented. If 60% of the candles are round, what is the probability that a candle selected randomly from the box will be unscented?
(1) If a candle is scented, it has an 80% chance of being round.
(2) If a candle is square, it has a 25% chance of being scented.
Source: Princeton Review
Organize the data in a DOUBLE-MATRIX.
Each candle in a particular box is either round or square and either scented or unscented.
60% of the candles are round.
The following matrix is yielded:
Question stem, rephrased:
What is the value of unscented/total?
Statement 1: If a candle is scented, it has an 80% chance of being round.
The following matrix is yielded:
No way to determine the value of unscented/total.
INSUFFICIENT.
Statement 2: If a candle is square, it has a 25% chance of being scented.
Thus, 1/4 of the 40 square candles -- in other words, 10 candles -- are both square and scented.
The following matrix is yielded:
No way to determine the value of unscented/total.
INSUFFICIENT.
Statements combined:
The following matrix is yielded:
The top of the middle column implies the following:
0.2x = 10
x = 50.
The following matrix is yielded:
Thus, unscented/total = 50/100.
SUFFICIENT.
The correct answer is
C.
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