DC Energy Interview Question: how many zeros are at the end... | Glassdoor

Interview Question

Investment Analyst Interview(Student Candidate) Washington, DC

how many zeros are at the end of 100!

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Interview Answer

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24. Count all multiples of 5, so 100/5=20, and multiples of 25(give you an additional 0) 100/25=4. This means 24 zeros. All other explanations are basically complicated ways of this fact.

Anonymous on Aug 23, 2011
2

An elaboration of the above: You are looking to build ten's since each time ten is multiplied by ten, the number of zero's increases by one. The prime factorization of ten is 5*2. In 100!, the determining factor in the number of ten's you can build is the number of fives (since two's are plentiful)...hence you are counting the number of fives in the prime factorization of 100!

Anonymous on Sep 17, 2012

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