Question: There are 8 books in a shelf that consist of 1 paperback books and 7 hardback books. If 4 books are selected at random without replacement, how many different combinations are there that at least one paperback book is selected?
Options:
(A) 35
(B) 45
(C) 50
(D) 55
(E) 60
Answer: 8C4 [Select any four] - 7C4 [Select all hard backs] = 35.
The answer is (A).

Question: Ten telegenic contestants with a variety of personality disorders are to be divided into two “tribes” of three members each, tribe A and tribe B, for a competition. How many distinct groupings of two tribes are possible?
Options:
(A) 120
(B) 126
(C) 252
(D) 1200
(E) 1260
Answer: My ans is 10C3 = 120
The answer is (A).

Question: 10 men and 15 women together can complete a work in 6 days. It takes 100 days for one man alone to complete the same work. How many days will be required for one woman alone to complete the same work?
Options:
(A) 127 days
(B) 667 days
(C) 177 days
(D) 187 days
(E) 225 days
Answer: 1 man's 1 day work = 1/100
(10 men + 15 women)'s 1 day work = 1/6
15 women's 1 day work = (1/6 - 10/100) = 1/15
1 woman's 1 day work = 1/225
1 woman alone can complete the work in 225 days.
The answer is (E).

Question: In a school of 450 boys, 44% of Muslims, 28% Hindus, 10% Sikhs and the remaining of other communities. How many belonged to the other communities?
Options:
(A) 72
(B) 75
(C) 80
(D) 81
(E) 90
Answer:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
44 + 28 + 10 = 82%
100 – 82 = 18%
450 * 18/100 = 81
The answer is (D).