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 â€śFactors of Factorialsâ€ť and â€śNON Factors of Factorialsâ€ť videos on PrepSwift.

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!

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.

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 â†’ [(50 - 4)/4 ] + 1 = 12.5 =12

4^2 = 16 â†’ [(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.