Question: The average of 9 observations was 9, that of the 1st of 5 being 10 and that of the last 5 being 8. What was the 5th observation?
Options:
(A) 9
(B) 8
(C) 7
(D) 6
(E) 2
Answer: 1 to 9 = 9 * 9 = 81
1 to 5 = 5 * 10 = 50
5 to 9 = 5 * 8 = 40
5th = 50 + 40 = 90 81 = 9
The answer is (A).

Question: A no. when divided by the sum of 555 and 445 gives 2times their difference as quotient & 50 as remainder. Find the no. is?
Options:
(A) 220060
(B) 145778
(C) 220050
(D) 220800
(E) 220030
Answer: (555 + 445) * 2 * 110 + 50 = 220000 + 50 = 220050
The answer is (C).

Question: The average of 20 numbers is zero. Of them, at the most, how many may be greater than zero?
Options:
(A) 22
(B) 28
(C) 29
(D) 20
(E) 21
Answer: Average of 20 numbers = 0
Sum of 20 numbers = (0 * 20) = 0
It is quite possible that 19 of these numbers may be positive and if their sum is a, then 20th number is (-a).
The answer is (D).

Question: Find the area of the quadrilateral of one of its diagonals is 20 cm and its off sets 9 cm and 6 cm?
Options:
(A) 328
(B) 150
(C) 279
(D) 277
(E) 267
Answer:
1/2 * 20(9 + 6) = 150 cm2
The answer is (B).