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Primes

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Primes

by MBA.Aspirant » Wed Jun 29, 2011 9:27 pm
*p is equal to the product of all the integers between 1 and p, inclusive. How many prime numbers are there between *7 + 3 and *7 + 7, inclusive?

A) None
B) One
C) Two
D) Three
E) Four
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by Frankenstein » Thu Jun 30, 2011 12:42 am
Hi,
*7 = 1.2.3.4.5.6.7
So, it is divisible by all numbers from 2 to 7
So, when we add any number from 3 to 7, the number will still be divisible by that number
*7+3 = 3(1.2.4.5.6.7 + 1)
*7+4 = 4(1.2.3.5.6.7 + 1)
.
.
*7+7 = 7(1.2.3.4.5.6 + 1)
So, there are no primes in the given set of numbers

Hence, A
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by winniethepooh » Thu Jun 30, 2011 12:51 am
Between *7 + 3 and *7 + 7 = 7! + 3 and 7! + 7 = 5043 and 5047 .As there are no prime numbers between 5043 and 5047 the answer is none.
Hence, A.
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by amit2k9 » Thu Jun 30, 2011 3:04 am
7! will have 4,5,6 which can be taken out as common factors.
hence A.
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