How can someone help with this query? Unsure how to even start! And if someone can also kindly reference which prep swift video I should watch to learn the basic in answering this question? Would it be remainder?
See the “Factors of Factorials” and “NON Factors of Factorials” videos on PrepSwift.
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Yes, this is the one you need to watch. In English, the question is asking:
How many times can we divide 500! by 7 and still get an integer?
Your goal is to figure out how many 7s are in 500!
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Thanks @Leaderboard and @ganesh . I have watched both videos. Can I check if my method is correct? I kind ignore the numbers after decimal for 7^1, 7^2 and 7^3 ie round them down
Correct.
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Apologies for reviving an old thread @Leaderboard. I came across another similar question - when I tried using the method above, somehow my answer is wrong. Do you know why?
My working:
4^1 = 4 → [(50 - 4)/4 ] + 1 = 12.5 =12
4^2 = 16 → [(50 - 16 / 16 ] + 1 = 3.1 = 3
Sum = 15.
4 is not a prime. Decompose 4^x in terms of power of a prime and try again.
Yes.
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