Reasoning: 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
Ans: (C)
Question: 10 books are placed at random in a shelf. The probability that a pair of books will always be together is -
Options:
(A) 1/5
(B) 1/3
(C) 1/4
(D) 118/2
(E) 21/4
Rationale: {Total} = {finance} + {marketing} - {both} + {neither}
100 = 25 + 55 - {both} + 40
{both} = 20%.
The answer: (D)
Question: Walking across campus, a student interviewed a group of students. 25% of the students took a finance class last semester, 55% took a marketing class last semester, and 40% took neither a finance nor a marketing class last semester. What percent of the students in the group took both a finance and a marketing class?
Options:
(A) 60%
(B) 50%
(C) 25%
(D) 20%
(E) 10%
Reasoning: Let the number of dogs be 'x' and the number of peacocks by 'y'. Then, number of legs in the group = 4x + 2y. Number of heads in the group = x+y So, 4x+2y = 4(x+y) 18 2y = 18 y = 9 Number of peacocks in that group = 9.
Ans: (A)
Question: In a group of dogs and peacocks, the number of legs are 18 less than four times the number of heads How many peacocks are there in that group?
Options:
(A) 9
(B) 8
(C) 7
(D) 6
(E) 5
Rationale: The sum of the first two (last two) digits cannot be 0 because 0000 is not a four-digit integer. If the sum of the first two digits is 1, two variants are possible: 1001 and 1010 (we have to remember that 0 cannot be the first digit). If the sum of the first two digits is 2, one variant is possible: 1111. In all, there are three numbers that satisfy the given conditions: 1001, 1010, and 1111.
The answer: (A)
Question: How many positive four-digit integers do not contain any digits other than 1 or 0 and are such that the sum of the first two digits equals the sum of the last two digits?
Options:
(A) 3
(B) 4
(C) 8
(D) 10
(E) 12
Reasoning: 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
Ans: (C)
Question: 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
Reasoning: Speed = 60 * 5/18 = 50/3 m/sec
Length of the train = speed * time = 50/3 * 3 = 50 m
Ans: (D)
Question: A train running at the speed of 60 km/hr crosses a pole in 3 sec. What is the length of the train?
Options:
(A) 85 m
(B) 70 m
(C) 115 m
(D) 50 m
(E) 150 m