Is it Prime?

Number Theory Level 1

How many numbers less than 20 are prime?

Details and assumptions

A number is prime if it has exactly 2 distinct divisors, 1 and itself.


The answer is 8.

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Arron Kau by Arron Kau

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3 solutions

List them all and count. 2 , 3 , 5 , 7 , 11 , 13 , 17 , 19 2,3,5,7,11,13,17,19 .It follows that there are 8 8 prime numbers less than 20 20 so the answer is 8 \boxed{8}

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the numbers are 2,3,5,7,11,13,17 and 19

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Eunice Stars
Aug 5, 2013

2;3;5;7;11;13;17;19

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how didi you get it?

Pjhay Nedamla - 7 years, 10 months ago

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