Ricky Wiryopranoto's answer to Candice lim's Secondary 3 A Maths Singapore question.
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Hi Candice, my answer is different from the one posted by Eric, maybe you can refer to the answer key.
Keys to my working are:
1. For every 5 incremental of factorial, you get additional zero because the whole sum is multiply by 10 or having 5 multiply by any past even number.
2. Then we need to consider when the number reach in the hundreds as at 100,200,300, etc, instead of multiply by 10, the whole number is multiply by 100. So there is additional zero introduced as compared to point no1
3. Same thing with thousands, instead of multiplying by 100, we multiply by 1000. Again there is introduction of additional zero.
Keys to my working are:
1. For every 5 incremental of factorial, you get additional zero because the whole sum is multiply by 10 or having 5 multiply by any past even number.
2. Then we need to consider when the number reach in the hundreds as at 100,200,300, etc, instead of multiply by 10, the whole number is multiply by 100. So there is additional zero introduced as compared to point no1
3. Same thing with thousands, instead of multiplying by 100, we multiply by 1000. Again there is introduction of additional zero.
Date Posted:
4 years ago
Your answer looks very logical. Maybe my answer is incorrect. But I am wondering what happens upon reaching 25! in your list, because apparently the multiplication of 25 introduces two zeroes (I think).
Say 24 * 25 = 600. Two zeroes are instantly introduced provided there are sufficient “2”s.
Say 24 * 25 = 600. Two zeroes are instantly introduced provided there are sufficient “2”s.
Thanks for your advice, Mr Ricky. I appreciate your time spent working on my question. Mr Eric's answer is correct, its 503.
Ah yes I forgot to consider that. Thanks for the enlightenment
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