LalaB wrote:A candy store attendant noticed that 45% of the kids bought coco-candy and orange-candy. However, 10% of the kids who bought coco-candy didn't order orange-candy. What is the probability that the next kid does not buy coco-candy?
(A) 35%
(B) 40%
(C) 45%
(D) 50%
(E) 55%
[spoiler]
didn't get why OE is 45+0.1x=x. could anyone show me the Venn diagram of this? [/spoiler]
ALWAYS LOOK AT THE ANSWER CHOICES.
The answer choices represent the percentage who DID NOT buy coco-candy.
The phrase
10% of the kids who bought coco-candy implies that the percentage who DID BUY coco-candy is a multiple of 10.
Thus, the correct answer is almost certainly either B (which implies that 60% bought coco-candy) or D (which implies that 50% bought coco-candy).
Let the total number of children = 100.
Answer choice D: 50% DID NOT buy coco-candy.
Thus, 50 kids DID BUY coco-candy.
Of these 50 kids who bought coco-candy, the 10% who DID NOT ALSO BUY orange-candy = .1(50) = 5.
Thus, the number who bought BOTH candies = 50-5 = 45.
Success! According to the problem, 45% bought both types of candy.
The correct answer is
D.
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