q: If the given two numbers are respectively 7% and 28% of a third number, then what percentage is the first of the second ?
Options:
(A) 20%
(B) 25%
(C) 18%
(D) 30%
(E) none of these
a: Stream of consciousness: Here, l = 7 and m = 28
Therefore, first number = l/m x 100% of second number = 7/28 x 100% of second number = 25% of second number The answer is (B).

question: The average of 13 numbers is 59. Average of the first 7 of them is 57 and that of the last 7 is 61. Find the 8th number?
Options:
(A) 59
(B) 83
(C) 45
(D) 53
(E) 64
answer: Stream of consciousness: Sum of all the 13 numbers = 13 * 59 = 767
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 - 767 = 59. The answer is (A).

q: At what rate percent on simple interest will a sum of money double itself in 30 years?
Options:
(A) 3 1/3%
(B) 3 1/6%
(C) 3 1/5%
(D) 3 5/3%
(E) 7 1/3%
a: Stream of consciousness: P = (P*30*R)/100
R = 3 1/3% The answer is (A).

question: The average age of a class of 32 students is 16 yrs. if the teacher's age is also included, the average increases by one year. Find the age of the teacher
Options:
(A) 34 Years
(B) 37 Years
(C) 49 Years
(D) 51 Years
(E) 57 Years
answer: Stream of consciousness: Total age of students is 32X16 = 512 Years
Total age inclusive of teacher = 33X (16+1) = 561
So, Teacher's age is 561-512 = 49 Yrs
There is a shortcut for these type of problems
Teacher's age is 16+(33X1) = 49 Years The answer is (C).

q: A train running at the speed of 60 km/hr crosses a pole in 12 sec. What is the length of the train?
Options:
(A) 356
(B) 200
(C) 127
(D) 279
(E) 150
a: Stream of consciousness: Speed = 60 * 5/18 = 50/3 m/sec
Length of the train = speed * time = 50/3 * 12 = 200 m The answer is (B).

q: Two trains are moving at 50 kmph and 70 kmph in opposite directions. Their lengths are 170 m and 100 m respectively. The time they will take to pass each other completely is?
Options:
(A) 3 sec
(B) 8 sec
(C) 9 sec
(D) 5 sec
(E) 7 sec
a:
Stream of consciousness: 70 + 50 = 120 * 5/18 = 100/3 mps
D = 170 + 100 = 270 m
T = 270 * 3/100 = 8 sec The answer is (B).