If d is appositive integer and f is the product of the first

[jurikondratev]

Data Sufficiency:
If d is appositive integer and f is the product of the first 30 positive integers, what is the value of d?
(1) 10^d is a factor of f
(2) d>6

Answer: C


We know that 2x5=10 and there are 10, 20, and 30 in teh product so I can count 6 mulptiples of 10 in teh product - ho wdo I get # 7 or 8 (or what ever d is)?

[tracerbullet]

is d 7? i think the answer would be C.

[joehurundas]

more like a weird approach:
1.2...5.6...10 => 1.2..(5)(6)...(10) = 1.60.3.4.7.8.9.10 (2.5.6 =60)
2 zero's here

11.12...15.16...20 => 11.(12.15.16).....20= 11.2880.13.14...20
also, 2 zeros' here

21.22...25.26...30=>21.(22.25.26)...30 = 21.14300.23.24...30
3 zero's here

counting the numbers of zero's above, you'll realize a maximum of 7
Someone with a better approach please.

[tracerbullet]

more like a weird approach:
1.2...5.6...10 => 1.2..(5)(6)...(10) = 1.60.3.4.7.8.9.10 (2.5.6 =60)
2 zero's here

11.12...15.16...20 => 11.(12.15.16).....20= 11.2880.13.14...20
also, 2 zeros' here

21.22...25.26...30=>21.(22.25.26)...30 = 21.14300.23.24...30
3 zero's here

counting the numbers of zero's above, you'll realize a maximum of 7
Someone with a better approach please.

I kind of did the same thing -

1 * 2 * 3....* 30 or 30! can be written as
2^(some number, obviously greater than 7) * 5 ^ 7 * Y(some number again)
which in turn can be written as
10^7 * Z

So we have d as 7

[RonPurewal]

there are already two big threads on this problem.

here you go:

post7466.html#p7466

post26005.html#p26005

if you still have questions after reading those threads, please post on one of THOSE threads (not on this thread).

thanks.