Rationale: Six persons can be arranged in a row in 6! ways. Treat the three persons to sit together as one unit then there four persons and they can be arranged in 4! ways. Again three persons can be arranged among them selves in 3! ways. Favourable outcomes = 3!4! Required probability = 3!4!/6! = 1/5
The answer: (C)
Question: If six persons sit in a row, then the probability that three particular persons are always together is ?
Options:
(A) 1/6
(B) 1/0
(C) 1/5
(D) 1/4
(E) 1/1
Reasoning: Saving = (42-32)% of 42400 = 4240.
Ans: (C)
Question: If the personal income tax rate is lowered from 42% to 32%, what is the differential savings for a tax payer having an annual income before tax to the tune of $42400?
Options:
(A) $3500
(B) $5000
(C) $4240
(D) $7000
(E) $10000
Rationale: Total age of 60 students
(45X 10+15 X 10) = 630
Average = 600/60 = 10 Years
The answer: (C)
Question: In a class, the average age of 45 boys is 10 years and the average of 15 girls is 10 years. what is the average age of the whole class?
Options:
(A) 12 Years
(B) 12.3 Years
(C) 10 Years
(D) 13 Years
(E) 15 Years
Reasoning: The probability of selecting girl is: 20/100 = 1/5
The probability of selecting rich is: 20/100 = 1/5
The probability of selecting fair complexioned is: 40/100 = 2/5
Three are independent;probability of rich and fair complexioned girl is:
(1/5) (1/5) (2/5) = 2/125
Ans: (A)
Question: A class consists of 100 students, 20 of them are girls and 80 boys; 20 of them are rich and remaining poor; 40 of them are fair complexioned. The probability of selecting a fair complexioned rich girl is
Options:
(A) 2/125
(B) 1/59
(C) 1/56
(D) 1/54
(E) 1/53
Rationale: Sum of all the 13 numbers = 13 * 60 = 780
Sum of the first 7 of them = 7 * 57 = 399
Sum of the last 7 of them = 7 * 61 = 427
So, the 8th number = 427 + 399 - 780 = 46.
The answer: (A)
Question: The average of 13 numbers is 60. Average of the first 7 of them is 57 and that of the last 7 is 61. Find the 8th number?
Options:
(A) 46
(B) 83
(C) 45
(D) 53
(E) 64
Rationale: 1: 2/5 = 5: 2
2/7 * 28 = 8
The answer: (B)
Question: A 28 cm long wire is to be cut into two pieces so that one piece will be 2/5th of the other, how many centimeters will the shorter piece be?
Options:
(A) 12
(B) 8
(C) 88
(D) 77
(E) 14