q: There are 7 fictions and 6 non-fictions. How many cases are there such that 2 fictions and 2 non-fictions are selected from them?
Options:
(A) 90
(B) 120
(C) 315
(D) 180
(E) 200
a: Stream of consciousness: Number of ways of selecting 2 fiction books = 7C2
Number of ways of selecting 2 non fiction books = 6C2
7C2 * 6C2 = 21 * 15 = 315 The answer is (C).
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q: The distance between West-Town to East-Town is 14 kilometers. Two birds start flying simultaneously towards one another, the first leaving from West-Town at a speed of 5 kilometers per minute and the second bird, leaving from East-Town, at a speed of 2 kilometers per minute. What will be the distance, in kilometers, between the meeting point and West-Town?
Options:
(A) 3.
(B) 7.
(C) 10.
(D) 12.
(E) 15.
a: Stream of consciousness: Time taken by the birds to meet = 14/(5+ 2) = 2 mins
Distance traveled by the bird traveling from West-Town = 5 * 2 = 10 The answer is (C).
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q: Out of 15 consecutive numbers, 2 are chosen at random. The probability that they are both odds or both primes is
Options:
(A) 10/17
(B) 10/19
(C) 46/105
(D) 11/15
(E) Cannot be determined
a:
Stream of consciousness: There is no definite formula for finding prime numbers among 15 consecutive numbers. Hence the probability cannot be determined. The answer is (E).
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