Q: A and B can do a work in 10 days and 15 days respectively. A starts the work and B joins him after 3 days. In how many days can they complete the remaining work?
Options:
(A) 6 days
(B) 2 days
(C) 8 days
(D) 4 1/5 days
(E) 9 days
A: OK... Stream of consciousness: Work done by A in 3 days = 3/10
Remaining work = 7/10
Work done by both A and B in one day = 1/10 + 1/15 = 5/30 = 1/6
Remaining work = 7/10 * 6/1 = 21/5 = 4 1/5 days.
The answer is (D).

Q: In how many different ways can the letters of the word ‘PREPTY’ be arranged?
Options:
(A) 230
(B) 240
(C) 260
(D) 280
(E) 360
A: OK... Stream of consciousness: Number of ways = 61/21 6X5X4X3X2X1 - 360
The answer is (E).

Q: The average of first six prime numbers greater than 20 is?
Options:
(A) 10
(B) 20
(C) 30
(D) 40
(E) 34
A: OK... Stream of consciousness: 23 + 29 + 31 + 37 + 41 + 43 = 204/6 = 34
The answer is (E).

Q: 4000 was divided into two parts such a way that when first part was invested at 3% and the second at 5%, the whole annual interest from both the investments is Rs.144, how much was put at 3%?
Options:
(A) 2808
(B) 2829
(C) 2800
(D) 2829
(E) 2821
A:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
OK... Stream of consciousness: (x*3*1)/100 + [(4000 - x)*5*1]/100 = 144
3x/100 + 200 – 5x/100 = 144
2x/100 = 56 è x = 2800
The answer is (C).