Question: If the given two numbers are respectively 8% and 16% of a third number, then what percentage is the first of the second ?
Options:
(A) 20%
(B) 25%
(C) 18%
(D) 50%
(E) none of these
Ans: (D)
CoT: Here, l = 8 and m = 16
Therefore, first number = l/m x 100% of second number = 8/16 x 100% of second number = 50% of second number
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Question: What percent is 120 of 70?
Options:
(A) 133 1/3 %
(B) 134 1/3 %
(C) 135 1/3 %
(D) 140 1/3 %
(E) 171 3/7 %
Ans: (E)
CoT: 120/70 = 12/7
12/7 100 = 1200/7 = 171 3/7 %
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Question: A can do a piece of work in 4 hours; B and C together can do it in 3 hours, which A and C together can do it in 2 hours. How long will B alone take to do it?
Options:
(A) 15 hours
(B) 14 hours
(C) 12 hours
(D) 74 hours
(E) 79 hours
Ans: (C)
CoT: A's 1 hour work = 1/4;
(B + C)'s 1 hour work = 1/3;
(A + C)'s 1 hour work = 1/2
(A + B + C)'s 1 hour work = (1/4 + 1/3) = 7/12
B's 1 hour work = (7/12 + 1/2) = 1/12
B alone will take 12 hours to do the work.
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