Please provide solutions for these set of PS questions.

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1) For every positive even integer n, the function h(n) is defined to be the product of all even integers from 2 to n inclusive. If p is the smallest prime factor of h(100) + 1, then p is between
a. 2 and 10
b. 10 and 20
c. 20 and 30
d. 30 and 40
e. > 40


2) 5 people are seated around a round table. Two seating arrangements are considered different only when the positions of the people are different relative to each other. What is the total number of different possible seating arrangements for the group?
a. 5
b. 10
c. 24
d. 32
e. 120


3) A set of 15 different integers has median of 25 and a range of 25. What is greatest possible integer that could be in this set?
a. 32
b. 37
c. 40
d. 43
e. 50
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by Anurag@Gurome » Thu Dec 15, 2011 11:09 pm
snakedoc wrote:1) For every positive even integer n, the function h(n) is defined to be the product of all even integers from 2 to n inclusive. If p is the smallest prime factor of h(100) + 1, then p is between
a. 2 and 10
b. 10 and 20
c. 20 and 30
d. 30 and 40
e. > 40

h(100) = 2 * 4 * 6 * ... * 100
= (2 * 1) * (2 * 2) * (2 * 3) * ... * (2 * 50)
= 2^(50) * (1 * 2 * 3 ... * 50)
Then h(100) + 1 = 2^(50) * (1 * 2 * 3 ... * 50) + 1
Now, h(100) + 1 cannot have any prime factors 50 or below, because dividing this value by any of these prime numbers will give a remainder of 1.

The correct answer is E.
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by Anurag@Gurome » Thu Dec 15, 2011 11:12 pm
snakedoc wrote: 2) 5 people are seated around a round table. Two seating arrangements are considered different only when the positions of the people are different relative to each other. What is the total number of different possible seating arrangements for the group?
a. 5
b. 10
c. 24
d. 32
e. 120
For any number N, the circular permutation formula is (N - 1)!
N = 5
Total no. of different possible seating arrangements = (N - 1)! = 4! = 24

The correct answer is C.
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by Anurag@Gurome » Thu Dec 15, 2011 11:14 pm
snakedoc wrote: 3) A set of 15 different integers has median of 25 and a range of 25. What is greatest possible integer that could be in this set?
a. 32
b. 37
c. 40
d. 43
e. 50
Median of a set of 15 different integers will be the 8th integer of the series when arranged according to their values.

Now, Largest - Smallest = Range => Largest = (Smallest + Range)
As the range is fixed, we can maximize largest number by maximizing the smallest number.

Maximum possible value of the smallest integer in the set is (25 - 7) = 18, as all the terms are different and 25 is the 8th term.

Hence, greatest possible integer in the set = (18 + Range) = (18 + 25) = 43

The correct answer is D.
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