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In each production lot for a certain toy, 25 percent of the [#permalink]
24 Mar 2008, 12:36
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In each production lot for a certain toy, 25 percent of the toys are red and 75 percent of the toys are blue. Half the toys are size A and half are size B. If 10 out of a lot of 100 toys are red and size A, how many of the toys are blue and size B? (A) 15 (B) 25 (C) 30 (D) 35 (E) 40
Given 100 Toys in total. So toal read toys = 25 Total blue toys = 75 Total size A = 50 Total size B = 50 Total Red and Size A = 10 So Remaining Red toys will be all size B = 25 - 10 = 15 Remaining Size B toys which must come from Blue toys = 50 - 15 = 35
You cannot multiply as you did because It is not necessary that half of red toys are size A and remaining half are size B. Similarly it is also not necessary that half of blue toys are size A and remaining half are size B. But by your calculation you are assuming just that. Thereby the flaw.