q: A bag contains 3 red and 2 black ball. Another bag contains 4 red and 5 black balls. A ball is drawn from the first bag and is placed in the second. A ball is then drawn from the second. What is the probability that this draw of red ball is due to the drawing of red ball from the first bag ?
Options:
(A) 3/5
(B) 2/5
(C) 4/25
(D) 3/10
(E) 15/23
a: OK... Probability of getting red ball from bag1 and then red from bag 2 = 3/5*5/10 = 15/50
Probability of getting black ball from bag1 and then red from bag 2 = 2/5*4/10 = 8/50
Now comes the condition, hence apply conditional probability:
P(Red)/ P(Red + Black)
(15/50)/(15/50+8/50) = 15/50 /23/50 = 15/23.
The answer is (E).

q: In a school of 850 boys, 40% of Muslims, 28% Hindus, 10% Sikhs and the remaining of other communities. How many belonged to the other communities?
Options:
(A) A) 125
(B) B) 627
(C) C) 187
(D) D) 721
(E) E) 159
a: OK... 40 + 28 + 10 = 78%
100 78 = 22%
850 * 22/100 = 187
The answer is (C).

q: Look at this series: 8, 43, 11, 41, __, 39, 17, ... What number should fill in the blank?
Options:
(A) 8
(B) 14
(C) 43
(D) 44
(E) 9
a:
OK... Answer: Option B
This is a simple alternating addition and subtraction series. The first series begins with 8 and adds 3; the second begins with 43 and subtracts 2.
The answer is (B).