Bunuel
If n is a positive integer, how many positive odd factors does it have ?
(1) The highest integer power of 2, that divides n is 16.
(2) n has a total of 68 factors and 3 prime factors.
How many odd positive integers divide the positive integer n completely?
(1) 16 is the highest power of 2 that divides n
(2) n has a total of 68 factors and 3 prime factors.
Statement 1This tells us that n will have 2 as one of the factors, but does not tell us anything about other factors (whether are any or not, let alone how many)
Not sufficient.Statement 2This just tells us that n has a total of 68 factors and only 3 prime factors.
If we factorize 68, we get : 68 = \(2^2 . 17^1\)
Using this -
If n has all 3 odd prime factors : 3, 7, and 11
We can get 68 prime factors : 3^16 . \(7^1 . 11^1\)
If n has one even prime factor and 2 odd prime factors
We can get 68 prime factors : 2^16 . \(7^1 . 11^1\)
Not sufficient.Combined togetherWe know one of the factors is 2 using statement 1, and statement 2 tells us that n has 3 prime factors.
Only 2 is an even prime number, all the other prime numbers are odd.
Using this property we can say that n has 2 odd prime factors.
Sufficient.Therefore, C.