q: The average of 13 numbers is 60. Average of the first 6 of them is 57 and that of the last 8 is 61. Find the 8th number?
Options:
(A) 46
(B) 48
(C) 50
(D) 52
(E) 54
a: Stream of consciousness: Sum of all the 13 numbers = 13 * 60 = 780
Sum of the first 6 of them = 6 * 57 = 342
Sum of the last 8 of them = 8 * 61 = 488
So, the 8th number = 342 + 488 - 780 = 50. The answer is (C).
--
q: There are 25 balls in a jar. You take out 5 blue balls without putting them back inside, and now the probability of pulling out a blue ball is 1/5. How many blue balls were there in the beginning?
Options:
(A) 12.
(B) 9.
(C) 8.
(D) 7.
(E) 6.
a: Stream of consciousness: 9 = 5 blue balls + 20/ 5 The answer is (B).
--
q: How many terminating zeroes R does 200! have?
Options:
(A) 40
(B) 48
(C) 49
(D) 55
(E) 64
a:
Stream of consciousness: You have 40 multiples of 5, 8 of 25 and 1 of 125. This will give 49 zeros. The answer is (C).
--