question: The average age of a class of 12 students is 8 yrs. if the teacher's age is also included, the average increases by one year. Find the age of the teacher
Options:
(A) 30 Years
(B) 31 Years
(C) 21 Years
(D) 34 Years
(E) 49 Years
answer: Stream of consciousness: Total age of students is 12X8 = 96 Years
Total age inclusive of teacher = 13X (8+1) = 117
So, Teacher's age is 117-96 = 21 Yrs
There is a shortcut for these type of problems
Teacher's age is 8+(13X1) = 21 Years The answer is (C).

q: Two pipes A and B can fill a cistern in 37 minutes and 45 minutes respectively. Both pipes are opened. The cistern will be filled in just half an hour, if the B is turned off after:
Options:
(A) 9
(B) 7
(C) 6
(D) 5
(E) 4
a: Stream of consciousness: Let B be turned off after x minutes. Then, Part filled by (A + B) in x min. + Part filled by A in (30 -x) min. = 1. x(2/75 + 1/45) + (30 - x). 2/75 = 1 11x/225 + (60 - 2x)/75 = 1 11x + 180 - 6x = 225. x = 9. The answer is (A).

question: Three 6 faced dice are thrown together. The probability that exactly two dice show the same number on them is?
Options:
(A) 5/15
(B) 5/12
(C) 5/19
(D) 5/12
(E) 5/11
answer: Stream of consciousness: Using question number 11 and 12, we get the probability as
1 - (1/36 + 5/9) = 5/12 The answer is (B).

q: Ravi can do a piece of work in 15 days while Prakash can do it in 30 days. In how many days will they finish it together?
Options:
(A) 11 days
(B) 9 days
(C) 8 days
(D) 12 days
(E) 10 days
a: Stream of consciousness: 1/15 + 1/30 = 3/30
10/1 = 10 days The answer is (E).

question: The average of fifteen results is 593 and that of the first fourteen is 594. The fifteenth result is?
Options:
(A) 575
(B) 602
(C) 579
(D) 586
(E) 592
answer: Stream of consciousness: 15 * 593 14 * 594 = 579 The answer is (C).

question: A car finishes a journey in nine hours at the speed of 80 km/hr. If the same distance is to be covered in six hours how much more speed does the car have to gain?
Options:
(A) 8 km/hr
(B) 40 km/hr
(C) 12 km/hr
(D) 16 km/hr
(E) None of these
answer:
Stream of consciousness: Distance covered by the car = 80 9 = 720 km
\ Speed = 7206 = 120 km/hr
\ Speed gain = 120 80 = 40 km/hr The answer is (B).