Ques: Two persons A and B can complete a piece of work in 30 days and 45 days respectively. If they work together, what part of the work will be completed in 4 days?
Options:
(A) 2/5
(B) 1/6
(C) 1/4
(D) 1/9
(E) 2/9
Ans: (E)
CoT: A's one day's work = 1/30
B's one day's work = 1/45
(A + B)'s one day's work = 1/30 + 1/45 = 1/18
The part of the work completed in 4 days = 4 (1/18) = 2/9.

Ques: An enterprising businessman earns an income of Re 5 on the first day of his business. On every subsequent day, he earns an income which is just thrice of that made on the previous day. On the 10th day of business, he earns an income of:
Options:
(A) 21
(B) 22
(C) 20
(D) 45
(E) 30
Ans: (D)
CoT: 2nd day he earns = 3(2 5)
3rd day he earns = 3(3 5)
On 20th day he earns 3(20 -5) = 45 rupees

Ques: Find the mean proportional between 64 & 81?
Options:
(A) A) 59
(B) B) 61
(C) C) 63
(D) D) 72
(E) E) 67
Ans: (D)
CoT: Formula = ab
A = 64 and B = 81
6481 = 8 9 = 72

Ques: The average of seven numbers is 18. The average of first three numbers is 14 and the average of last three numbers is 16. What is the middle number?
Options:
(A) 27
(B) 29
(C) 36
(D) 34
(E) 35
Ans: (C)
CoT: The total of seven numbers = 7X18 = 126
The total of first 3 and last 3 numbers is = 3 X 14+3 X 16 = 90
So, the middle number is (126 - 90 ) = 36