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If a light bulb is selected at random from a shipment, what is the probability that the light bulb is defective?

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If a light bulb is selected at random from a shipment, what is the probability that the light bulb is defective?

by BTGmoderatorDC » Wed Feb 26, 2020 7:16 pm

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If a light bulb is selected at random from a shipment, what is the probability that the light bulb is defective?

(1) The ratio of the number of defective light bulbs to the number of nondefective light bulbs is 1 to 60.

(2) The shipment contains 720 light bulbs.



OA A

Source: Magoosh
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Source: — Data Sufficiency |

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Re: If a light bulb is selected at random from a shipment, what is the probability that the light bulb is defective?

by Jay@ManhattanReview » Thu Feb 27, 2020 9:28 pm

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BTGmoderatorDC wrote: ↑
Wed Feb 26, 2020 7:16 pm
 If a light bulb is selected at random from a shipment, what is the probability that the light bulb is defective?

(1) The ratio of the number of defective light bulbs to the number of nondefective light bulbs is 1 to 60.

(2) The shipment contains 720 light bulbs.

OA A

Source: Magoosh
Let's take each statement one by one.

(1) The ratio of the number of defective light bulbs to the number of nondefective light bulbs is 1 to 60.

Say # of defective bulbs = x; thus, # of nondefective bulbs = 60x and the total no. of bulbs = 61x;

Probability that the light bulb is defective = x/61x = 1/61. Sufficient.

(2) The shipment contains 720 light bulbs.

Certainly insufficient.

The correct answer: A

Hope this helps!

-Jay
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