Rationale: One day work of A and B = 1/6
One day work of B and C = 1/2
One day work of C and A = 1/8
2(A + B + C) = 1/6 + 1/2 + 1/8
2(A + B + C) = 19/24
(A + B + C) = 19/48
Number of days required = 48/19 days.
The answer: (D)
Question: A and B can do a work in 6 days, B and C in 2 days and C and A in 8 days. In how many days will the work be completed, if all three of them work together?
Options:
(A) 12/24
(B) 48/63
(C) 45/56
(D) 48/19
(E) 28/12
Reasoning: Total number of ways = 7!*2!.
Ans: (B)
Question: There are 10person among whom 2are brother. The total no.of ways in which these persons can be seated around a round table so that exactly 1person sit between the brothers, is equal to?
Options:
(A) 7!
(B) 7!*2!
(C) 7!*3!
(D) 8!*1!
(E) 8!*4!
Rationale: D = 90 * 5/18 * 5 = 125 m
The answer: (B)
Question: If a train, travelling at a speed of 90 kmph, crosses a pole in 5 sec, then the length of train is?
Options:
(A) 288
(B) 125
(C) 88
(D) 76
(E) 232
Reasoning: 30^n = 2^n * 3^n * 5^n
100! has 97 2's, 48 3's and 24 5's
Since each of 2, 3 and 5 is required to form 30 and there are only 24 5's there can only be 24 30's in 100!
Ans: (B)
Question: If 100!/30^n is an integer, which of the following is the greatest possible value of n?
Options:
(A) 28
(B) 24
(C) 20
(D) 15
(E) 10
Rationale: The differences between two successive terms from the beginning are 7, 5, 7, 5, 7, 5. So, 40 is wrong.
The answer: (C)
Question: Find the invalid no.from the following series 13, 18, 25, 30, 37, 40
Options:
(A) 13
(B) 18
(C) 40
(D) 30
(E) 37
Rationale: The sum all three digits comes to 10 except 326
The answer: (A)
Question: Find the odd man out
253, 136, 352, 326, 631, 244
Options:
(A) 326
(B) 136
(C) 352
(D) 631
(E) 531