Rationale: Formula = Third proportional = (b b)/a
A = 4 and B = 16
(16 16)/ 4 = 256/4 = 64
The answer: (C)
Question: Find the third proportional to 4 and 16?
Options:
(A) 80
(B) 12
(C) 64
(D) 78
(E) 72
Reasoning: 1/20 - 1/28 = 1/70
70 minutes
Ans: (C)
Question: A pipe can fill a cistern in 20 minutes whereas the cistern when fill can be emptied by a leak in 28 minutes. When both pipes are opened, find when the cistern will be full?
Options:
(A) 76 minutes
(B) 29 minutes
(C) 70 minutes
(D) 17 minutes
(E) 98 minutes
Rationale: Each of the numbers except 21 is an even number
The answer: (C)
Question: 10, 14, 16, 18, 21, 24, 26
Options:
(A) 17
(B) 20
(C) 21
(D) 25
(E) 26
Reasoning: Sum of all the 13 numbers = 13 * 60 = 780
Sum of the first 7 of them = 7 * 54 = 378
Sum of the last 7 of them = 7 * 61 = 427
So, the 8th number = 427 + 378 - 780 = 25.
Ans: (A)
Question: The average of 13 numbers is 60. Average of the first 7 of them is 54 and that of the last 7 is 61. Find the 8th number?
Options:
(A) 25
(B) 83
(C) 45
(D) 53
(E) 64
Rationale: Sum of the terms of the ratio = 3 + 4 = 7
Sum of numbers = 63
Therefore, first number = 3/7 63 = 27
Second number = 4/7 63 = 36
Therefore, the two numbers are 27 and 36.
The answer: (C)
Question: Two numbers are in the ratio 3 : 4. If the sum of numbers is 63, find the numbers.
Options:
(A) 26,37
(B) 25,38
(C) 27,36
(D) 28,35
(E) 29,34
Rationale: Using question number 11 and 12, we get the probability as
1 - (1/36 + 5/9) = 5/12
The answer: (B)
Question: Three 6 faced dice are thrown together. The probability that exactly two dice show the same number on them is
Options:
(A) 5/54
(B) 5/12
(C) 5/17
(D) 5/18
(E) 5/14