Question: During a particular baseball game, the probability of a team's pitcher throwing a strike on each throw is 2/5. What is the least number of times that the pitcher should pitch the ball that will increase the probability of getting a strike at least once to more than 50%.
Options:
(A) 3
(B) 2
(C) 1
(D) 4
(E) 5
Answer: Rule of Subtraction: P(A) = 1 - P(A')
Rule of Multiplication: P(A B) = P(A) P(B)
The probability that the pitcher throws a strike at least once in 2 guesses is 1- (3/5)^2 = 1 - 9/25 = 16/25 > 50%.
The answer is (B).

Question: Every Sunday, Giri jogs 3 miles. For the rest of the week, each day he jogs 1 mile more than the previous day. How many miles does giri jog in 2 weeks ?
Options:
(A) 42
(B) 63
(C) 84
(D) 98
(E) 108
Answer: In one week, Giri jogs 3 + 4 + 5 + 6 + 7 + 8 + 9 = 42 miles
In two weeks, Giri jogs 84 miles.
The answer is (C).

Question: If 20m n = p, then which of the following represents the average (arithmetic mean) of m, n, and p, in terms of m?
Options:
(A) 2m 1
(B) 4m
(C) 6m
(D) 7m
(E) 6m/5
Answer: 20m - n = p
Add n to both sides:
20m = n + p
Add m to both sides:
21m = n + p + m
Now, divide both sides by 3
7m = (n + p + m)/3 = the average of n, p, and m
The answer is (D).

Question: What is theleast number should be added to 1056, so the sum of the number is completely divisible by 23?
Options:
(A) 20
(B) 23
(C) 25
(D) 27
(E) 28
Answer:
(1056 / 23) gives remainder 21
21 + 2 = 23, So we need to add 2
The answer is (B).