[Ques]: The average of five results is 48 and that of the first four is 45. The fifth result is?
Options:
(A) 50
(B) 60
(C) 70
(D) 80
(E) 90
*Ans*: (B)
--CoT--: 5 * 48 4 * 45 = 60

[Ques]: Two pipes can fill a tank in 20 and 24 minutes respectively and a waste pipe can empty 3 gallons per minute. All the three pipes working together can fill the tank in 15 minutes. The capacity of the tank is?
Options:
(A) 60 gallons
(B) 100 gallons
(C) 120 gallons
(D) 180 gallons
(E) 130 gallons
*Ans*: (C)
--CoT--: Work done by the waste pipe in 1 minute = 1/15 - (1/20 + 1/24) = - 1/40
Volume of 1/40 part = 3 gallonsVolume of whole = 3 * 40 = 120 gallons.

[Ques]: A bag contains nine black balls, three red balls and four red balls. In how many ways can two balls be drawn from the bag?
Options:
(A) C
(B) C
(C) C
(D) C
(E) C
*Ans*: (A)
--CoT--: Total number of balls = 9 + 3 + 4
Two balls can be drawn from 16 balls in C ways.

[Ques]: A and B can do a work in 2 days, B and C in 6 days and C and A in 8 days. In how many days will the work be completed, if all three of them work together?
Options:
(A) 12/28
(B) 48/19
(C) 16/48
(D) 18/48
(E) 12/64
*Ans*: (B)
--CoT--: One day work of A and B = 1/2
One day work of B and C = 1/6
One day work of C and A = 1/8
2(A + B + C) = 1/2 + 1/6 + 1/8
2(A + B + C) = 19/24
(A + B + C) = 19/48
Number of days required = 48/19 days.