Question: Ravi can do a piece of work in 15 days while Prakash can do it in 6 days. In how many days will they finish it together?
Options:
(A) 5 7/9 days
(B) 6 7/9 days
(C) 5 1/9 days
(D) 5 7/2 days
(E) 4 2/7 days
Answer: 1/15 + 1/6 = 7/30
30/7 = 4 2/7 days
The answer is (E).

Question: Find the invalid no.from the following series 13, 18, 25, 30, 37, 40
Options:
(A) 21
(B) 25
(C) 40
(D) 47
(E) 58
Answer: The differences between two successive terms from the beginning are 7, 5, 7, 5, 7, 5. So, 40 is wrong.
The answer is (C).

Question: Calculate the value of n from the below equation: n^310n+20=44
Options:
(A) 1
(B) 5
(C) 3
(D) 2
(E) 4
Answer: Use elimination method to find the correct option. you find that of all the options when 4 is the correct value for n
The answer is (E).

Question: The length W of a rectangle is decreased by 15% and its width is increased by 40%. Does the area of the rectangle decrease or increase and by what percent?
Options:
(A) Decreases by 19%
(B) Decreases by 25%
(C) Increases by 6%
(D) Increases by 19%
(E) Increases by 25%
Answer:
Let the length W of the rectangle be 100x, and width be 100y. Area = 100x * 100y = 10000xy
Now after the change Length = 85x, and width = 140 y. Area = 11900xy
% Change = (11900xy - 10000xy)/(10000xy) = 19 % Increase. Hence
The answer is (D).