Question

The number of numbers less than or equal to 666 which are the products of exactly 4 distinct positive prime numbers is:

• A. 4
• B. 8
• C. 7
• D. can't be determined

Answer 1

The correct option is C 7

$666=2\times 3^2\times 37$
Now, following are the cases possible for different integer values of a, b, c, d:
$1.2^a\times 3^b\times 5^c\times 7^{d}2.2^a\times 3^b\times 5^c\times {11}^{d}3.2^a\times 3^b\times 5^c\times {13}^{d}4.2^a\times 3^b\times 5^c\times {17}^{d}5.2^a\times 3^b\times 5^c\times {19}^{d}6.2^a\times 3^b\times 7^c\times {11}^{d}7.2^a\times 3^b\times 7^c\times {13}^d$