question: 80 370 ? 1550 2440 3530
Options:
(A) 900
(B) 840
(C) 750
(D) 860
(E) 960
answer: Stream of consciousness: 10^2 - 20 = 80
20^2 - 30 = 370
30^2 - 40 = 860
40^2 - 50 = 1550
50^2 - 60 = 2440
60^2 - 70 = 3530. The answer is (D).

q: In a certain lottery drawing, two balls are selected at random from a container with 10 balls, numbered from 1 to 10, inclusive. If the winner of the lottery is awarded a cash prize in the amount of $1,000 times the product of the numbers on the two selected balls, which of the following is a possible amount of the cash prize given to the winner?
Options:
(A) $9 x 10^4
(B) $9.90 x 10^6
(C) $1.00 x 10^7
(D) $1.05 x 10^7
(E) $9.90 x 10^7
a: Stream of consciousness: The max product of any two balls can be 9 * 10 = 9900 = 9 * 10
If we multiply it by $1000 the max amount will be 9 * 10^4. The answer is (A).

question: Find the third proportional to 3 and 9?
Options:
(A) 10
(B) 12
(C) 27
(D) 19
(E) 20
answer: Stream of consciousness: Formula = Third proportional = (b b)/a
A = 3 and B = 9
(9 x 9)/ 3 = 81/3 = 27 The answer is (C).

q: 10 books are placed at random in a shelf. The probability that a pair of books will always be together i
Options:
(A) 1/6
(B) 1/0
(C) 1/5
(D) 1/2
(E) 1/1
a: Stream of consciousness: 10 books can be rearranged in 10! ways consider the two books taken as a pair then number of favourable ways of getting these two books together is 9! 2!
Required probability = 1/5 The answer is (C).

question: Which of the following is a prime number ?
Options:
(A) 27
(B) 45
(C) 97
(D) 98
(E) 100
answer: Stream of consciousness: Clearly, 97 is a prime number. The answer is (C).

question: The probability is 1/2 that a certain coin will turn up heads on any given toss. If the coin is to be tossed three times, what is the probability that on at least one of the tosses the coin will turn up tails?
Options:
(A) 1/8
(B) 1/2
(C) 3/4
(D) 7/8
(E) 15/16
answer:
Stream of consciousness: P(at last 1 tails) = 1 - P(all heads) = 1 - (1/2)^3 = 7/8. The answer is (D).