GeminiHeat wrote:
g(x) is defined as the product of all even integers k such that 0 < k ≤ x. For example, g(14) = 2 × 4 × 6 × 8 × 10 × 12 × 14. If g(y) is divisible by 4^11, what is the smallest possible value for y?
(A) 22
(B) 24
(C) 28
(D) 32
(E) 44
g(x)=g(y) =x!/4^11=x!/2^22
test all answer choices to find
2n and
n=22:
(A)
22!/2n,
n=22/2+22/4+22/8+22/16=11+5+2+1=19 not a good choice
(B)
24!/2n,
n=24/2+24/4+24/8+24/16=12+6+3+1=22 a good choice
(C)
28!/2n,
n=28/2+28/4+28/8+28/16=14+7+3+1=25 not a good choice
choices (D) and (E) are not suitable as well. Hence, answer is
Bchecking the solution method and answer:
24=2∗4∗6∗8∗10∗12∗14∗16∗18∗20∗22∗24,
2=2^
1, 4=2^
2, 6=3*2^
1, 8=2^
3, 10=5*2^
1, 12=3*2^
2, 14=7*2^
1, 16=2^
4, 18=9*2^
1, 20=5*2^
2, 22=11*2^
1, 24=3*2^
3. Total powers of 2^
n result in
n=22