Eric Nicholas K's answer to Xiang Ning's Junior College 2 H2 Maths Singapore question.
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Might be wrong.
Date Posted:
4 years ago
The answer for the last part is 60 actually
The prime numbers also include 1 and 5?
Eh ya forgot that 5 is prime. Ouch, that was a primary mistake of mine. 1 is not prime.
Certainly if 3 of the prime numbers are prime, even though we can pick the first two digits as non-prime, the last digit by default is prime.
So all combinations of the numbers will be prime.
There are 60 numbers which are prime.
Certainly if 3 of the prime numbers are prime, even though we can pick the first two digits as non-prime, the last digit by default is prime.
So all combinations of the numbers will be prime.
There are 60 numbers which are prime.
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