Rationale: 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: (A)
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) 5
Reasoning: A's 1 hour work = 1/4;
(B + C)'s 1 hour work = 1/2;
(A + C)'s 1 hour work = 1/2
(A + B + C)'s 1 hour work = (1/4 + 1/2) = 3/4
B's 1 hour work = (3/4 - 1/2) = 1/4
B alone will take 4 hours to do the work.
Ans: (C)
Question: A can do a piece of work in 4 hours; B and C together can do it in 2 hours, which A and C together can do it in 2 hours. How long will B alone take to do it?
Options:
(A) 2hours
(B) 3hours
(C) 4hours
(D) 5hours
(E) 6hours
Rationale: Total members in the group = 7
Average amount = Rs. 20
Total amount with them = 7 * 20 = Rs. 140
One number has Rs. 50. So, the amount with remaining 6 people = 140 - 50 = Rs. 90
The average amount with them = 90/6 = Rs. 15.
The answer: (A)
Question: The average amount with a group of seven numbers is Rs. 20. If the newly joined member has Rs. 50 with him, what was the average amount with the group before his joining the group?
Options:
(A) 15
(B) 25
(C) 18
(D) 22
(E) 30
Reasoning: Rate of flow of water in second hour = 12 gallons per hour
Rate of flow of water in first hour = 12/(3/2) = 8 gallons per hour
Rate of flow of water in third hour = (125/100)* 12 = (5/4) * 12 = 15 gallons per hour
Number of gallons of water that flowed through the pipe during the entire 3 hours = 12+8+15 = 35 gallons
Ans: (D)
Question: The flow of water through a drainage pipe was monitored for a 3-hour period. In the second hour, the rate of flow was 12 gallons per hour, which was 50 percent faster than the rate of flow for the first hour. If 25 percent more water flowed through the pipe in the third hour than it did in the second, how many gallons of water flowed through the pipe during the entire three hours?
Options:
(A) 31.25
(B) 31.5
(C) 33.75
(D) 35.0
(E) 37.5
Rationale: Number of one digit numbers = 4
Number of two digit numbers = 4 P 2 = 12
Number of Three digit numbers = 4 P 3 = 24
Number of four digit numbers = 4 P 4 = 24
So, total = 24 + 24 + 12 + 4 = 64
The answer: (C)
Question: How many Numbers can be formed with digits 2,4,6,8 without repetition?
Options:
(A) 124
(B) 256
(C) 64
(D) 84
(E) 94
Rationale: D = 70 * 5/18 = 20 = 388 180 = 208
The answer: (A)
Question: A train 180 m long running at 70 kmph crosses a platform in 20 sec. What is the length of the platform?
Options:
(A) 208
(B) 277
(C) 350
(D) 881
(E) 271