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NDA 2019
Exam
NDA
Year
2019
Subject
Mathematics
Chapter
Permutation and Combination

NDA 2019 · Mathematics · Permutation and Combination

If n ! has 17 zeros, then what is the value of n ?

If nn ! has 17 zeros, then what is the value of nn ?

Options

  1. A95
  2. B85
  3. C80
  4. DNo such value of nn exists

Correct answer

D. No such value of nn exists

Step-by-step solution

∵\because number of zeroes = Highest power of 5. ∴\therefore by using options highest power in 95 is [955]+\left[\frac{95}{5}\right]+\left[\frac{95}{25}\right]+[95125]=21\left[\frac{95}{125}\right]=21 highest power in 80 is [805]+\left[\frac{80}{5}\right]+\left[\frac{80}{25}\right]=19highestpowerin85ishighest power in 85 is\left[\frac{85}{5}\right]+[8525]=19∴\left[\frac{85}{25}\right]=19\therefore option (D) no such value of nn exists.
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