Question: 189. The inside dimensions of a rectangular wooden box
are 10 inches by 12 inches by 14 inches. A cylindrical
canister is to be placed inside the box so that it stands
upright when the closed box rests on one of its six
faces. Of all such canisters that could be used, what is
the radius, in inches, of the one that has maximum
volume?
Options:
(A) 3
(B) 4
(C) 5
(D) 6
(E) 8
Ans: (D)
CoT: Since the radius is squared, the biggest volume cylinder will have the biggest possible radius. To achieve that, let the smaller dimension of the rectangular box be the height. So, it will have 14x12 width x length. The biggest cylinder must fit both dimensions, so it must have at most a diameter of 12, so the radius will be 6.
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Question: An analyst will recommend a combination of 2 industrial stocks, 2 transportation stocks, and 2 utility stocks. If the analyst can choose from 5 industrial stocks, 4 transportation stocks, and 3 utility stocks, how many different combinations of 6 stocks are possible?
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Options:
(A) 12
(B) 19
(C) 60
(D) 180
(E) 720
Ans: (D)
CoT: 5C2 * 4C2 * 3C2 = 10*6*3 = 180.
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Question: Solve:-
333 x 333 x 333 + 555 x 555 x 555 = ?(333 x 333 - 333 x 555 + 555 x 555)
Options:
(A) 888
(B) 333
(C) 555
(D) 988
(E) 889
Ans: (A)
CoT: Given Exp. = (a3 + b3) = (a + b) = (333 + 555) = 888(a2 - ab + b2)
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