q: Which of the following CANNOT be weighed using a balance scale and these unit weights: 2, 4, 7, and 10
Options:
(A) 16
(B) 15
(C) 18
(D) 19
(E) 21
a: Stream of consciousness: A. 13 (can be weighed by keeping weights of 10, 2 and 4 )
B. 15 (cannot be weighed)
C. 17 (can be weighed by keeping weights of 10 and 7 kg)
D. 19(can be weighed by keeping weights of 10, 2 and 7 kg)
E. 21 (can be weighed by keeping weights of 10, 7 and 4 kg) The answer is (B).
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q: A girl is organizing her jellybean collection in which each color has its own row. In each row, there are as many jellybeans as the number of jellybean colors. Her little brother chops each jellybean into the same number of peices as the number of jellybean colors. If the final number of jellybean pieces is m, then:
Options:
(A) m is a perfect square
(B) m is an odd number
(C) m is an even number
(D) m is a perfect cube.
(E) None
a: Stream of consciousness: For example, if there were 4 jellybean colors, the girl would have made a 4x4 arrangement. The boy chopped up each jellybean into 4, the number of pieces would be (4*4)*4 = 64 pieces, which is a cube of 4. The answer is (D).
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q: Four of the following five parts numbered (a), (b), (c), (d) and (e) in the following equation are exactly equal. Which of the parts is not equal to the other four? The number of that part is the answer.
Options:
(A) xy2 x2y + 2x2y2
(B) xy2(1 2x) + x2y(2y 1)
(C) xy2(1 + x) x2y(1 y)
(D) xy[y(1 + x) x(1 y) ]
(E) xy(y x + 2xy)
a:
Stream of consciousness: The other parts are equal to xy2 x2y + 2x2y2. The answer is (B).
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