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Number Theory

Level 4 / foundation

Primes (100-500)

3 visual steps / prime trial tests

1. Limit tests

prime? 2211. Limit testsOnly test primes up to sqrt.1sqrt(221) is under 15213 x 17 = 2213not prime
Only test primes up to sqrt.

Only test primes up to sqrt.

2. Try primes

prime? 2212. Try primesCheck the small prime divisors.1sqrt(221) is under 15213 x 17 = 2213not prime
Check the small prime divisors.

Check the small prime divisors.

3. Decide

prime? 2213. DecideStop when every test fails.1sqrt(221) is under 15213 x 17 = 2213not prime
Stop when every test fails.

Stop when every test fails.

Practice Level 4

Use the visible move, then type only when the answer is clear.

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