Rationale: 1/20 + 1/30 - 1/40 = 7/120
120/7 = 17 1/7
The answer: (C)
Question: Two pipes A and B can fill a cistern in 20 and 30 minutes respectively, and a third pipe C can empty it in 40 minutes. How long will it take to fill the cistern if all the three are opened at the same time?
Options:
(A) 17 1/5
(B) 17 1/8
(C) 17 1/7
(D) 17 1/1
(E) 17 1/2
Reasoning: Let the boys are X, then girls are 7X, total = X+7X = 8X
So it should be multiple of 8, 30 is not a multiple of 8.
Ans: (C)
Question: The no. of girls in a class are 7times the no. of boys, which value cannever be the of total students?
Options:
(A) 20
(B) 35
(C) 30
(D) 40
(E) 42
Rationale: 15 men using chain rul
The answer: (E)
Question: If 21 WOMen and 12 men can finish the work in 42 days.How many men should accompany 42 women to that the work will be completed in ten and half days???
Options:
(A) 40
(B) 45
(C) 50
(D) 60
(E) 15
Reasoning: Sum of 13 natural no. = 182/2 = 91
Average = 91/13 = 7
Ans: (C)
Question: The average of first 13 natural numbers is?
Options:
(A) 5.2
(B) 5.5
(C) 7
(D) 9
(E) 10
Rationale: Cone curved surface area = rl = 22/7 4 5 = 440/7 = 62 6/7
Slant height (l) = r(power2)+h(power2) = 16+9 = 25 = 5
The answer: (C)
Question: The radius of a cone is 4 m, height 5 m. Find the curved surface area?
Options:
(A) 1
(B) 3
(C) 5
(D) 7
(E) 9
Rationale: Rule of Subtraction: P(A) = 1 - P(A')
Rule of Multiplication: P(A B) = P(A) P(B)
The probability that the quarterback throws a completed pass at least once in 2 throws is 1- (7/10)^2 = 1 - 49/100 = 51/100 > 50%
The answer: (C)
Question: For a particular American football game, the probability of a team's quarterback throwing a completed pass on each throw is 3/10. What is the least number of times that the quarterback should throw the ball that will increase the probability of getting a completed pass at least once to more than 50%.
Options:
(A) 10
(B) 5
(C) 2
(D) 3
(E) 1