Walkabout wrote:

A box contains only red chips, white chips, and blue chips. If a chip is randomly selected from the box, what is the probability that the chip will be either white or blue?

(1) The probability that the chip will be blue is 1/5.

(2) The probability that the chip will be red is 1/3.

Target question: What is the probability that the chip is either white or blue? Given: The box contains only red chips, white chips, and blue chips Statement 1: The probability that the chip will be blue is 1/5.This tells us that 1/5 of the chips are BLUE, but there's no information about the WHITE chips.

Consider these two possible cases:

Case a: There are 5 chips in total. 1 chip is blue, and 1 chip is white. In this case, the answer to the target question is

P(chip is either white or blue) = 2/5Case b: There are 5 chips in total. 1 chip is blue, and 2 chips are white. In this case, the answer to the target question is

P(chip is either white or blue) = 3/5Since we cannot answer the

target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: The probability that the chip will be red is 1/3 This also tells us that

the probability of selecting a NON-RED chip is 2/3Since the box contains only red chips, white chips, and blue chips, then selecting a NON-RED chip is the same as selecting either a BLUE chip OR a WHITE chip

In other other words, P(select NON-BLUE chip) = P(selecting either a BLUE chip OR a WHITE chip)

So, the answer to the target question is

P(chip is either white or blue) = 2/3Answer: B

Cheers,

Brent

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