saswatdodo wrote:
Bunuel wrote:
If d is a positive 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 -->\(k*10^d=30!\) .
First we should find out how many zeros\(30!\) has, it's called trailing zeros. It can be determined by the power of\(5\) in the number\(30!\) -->\(\frac{30}{5}+\frac{30}{25}=6+1=7\) -->\(30!\) has\(7\) zeros.
\(k*10^d=n*10^7\) , (where\(n\) is the product of other multiples of 30!) --> it tells us only that max possible value of\(d\) is\(7\) . Not sufficient.
Side notes:
(1) 10^d is a factor of f -->\(k*10^d=30!\) .
First we should find out how many zeros\(30!\) has, it's called trailing zeros. It can be determined by the power of\(5\) in the number\(30!\) -->\(\frac{30}{5}+\frac{30}{25}=6+1=7\) -->\(30!\) has\(7\) zeros.
\(k*10^d=n*10^7\) , (where\(n\) is the product of other multiples of 30!) --> it tells us only that max possible value of\(d\) is\(7\) . Not sufficient.
Side notes:
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