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Number Theory

Primes, factors, GCD, LCM, and divisibility rules - the building blocks of number sense.

To find GCD(a,b): repeatedly replace the larger with the remainder until 0. Then LCM = axb / GCD.

Level Guides

30 level-fit visual guides.

Level 1 visual plan for Primes (<= 30)

Level 1 / foundation

Primes (<= 30)

3 visual steps

Level 2 visual plan for Primes (<= 50)

Level 2 / foundation

Primes (<= 50)

3 visual steps

Level 3 visual plan for Primes (50-200)

Level 3 / realistic untimed

Primes (50-200)

3 visual steps

Level 4 visual plan for Primes (100-500)

Level 4 / foundation

Primes (100-500)

3 visual steps

Level 5 visual plan for Divisibility intro (2, 3, 5)

Level 5 / foundation

Divisibility intro (2, 3, 5)

3 visual steps

Level 6 visual plan for Divisibility (2-6)

Level 6 / foundation

Divisibility (2-6)

3 visual steps

Level 7 visual plan for Divisibility (3-9)

Level 7 / foundation

Divisibility (3-9)

3 visual steps

Level 8 visual plan for Divisibility (all small rules)

Level 8 / realistic untimed

Divisibility (all small rules)

3 visual steps

Level 9 visual plan for GCD (small, <= 30)

Level 9 / foundation

GCD (small, <= 30)

3 visual steps

Level 10 visual plan for GCD (<= 50)

Level 10 / foundation

GCD (<= 50)

3 visual steps

Level 11 visual plan for GCD (<= 80)

Level 11 / build-up

GCD (<= 80)

3 visual steps

Level 12 visual plan for GCD (<= 120)

Level 12 / build-up

GCD (<= 120)

3 visual steps

Level 13 visual plan for GCD (<= 200)

Level 13 / realistic untimed

GCD (<= 200)

3 visual steps

Level 14 visual plan for GCD (<= 300)

Level 14 / build-up

GCD (<= 300)

3 visual steps

Level 15 visual plan for GCD mastery (<= 500)

Level 15 / build-up

GCD mastery (<= 500)

3 visual steps

Level 16 visual plan for LCM (<= 12)

Level 16 / build-up

LCM (<= 12)

4 visual steps

Level 17 visual plan for LCM (<= 18)

Level 17 / build-up

LCM (<= 18)

4 visual steps

Level 18 visual plan for LCM (<= 25)

Level 18 / realistic untimed

LCM (<= 25)

4 visual steps

Level 19 visual plan for LCM (<= 35)

Level 19 / build-up

LCM (<= 35)

4 visual steps

Level 20 visual plan for LCM (<= 50)

Level 20 / build-up

LCM (<= 50)

4 visual steps

Level 21 visual plan for LCM (<= 60)

Level 21 / mastery

LCM (<= 60)

4 visual steps

Level 22 visual plan for LCM mastery (<= 80)

Level 22 / mastery

LCM mastery (<= 80)

4 visual steps

Level 23 visual plan for Rules - small (2, 3, 4, 5)

Level 23 / realistic untimed

Rules - small (2, 3, 4, 5)

3 visual steps

Level 24 visual plan for Rules - even (4, 6, 8)

Level 24 / mastery

Rules - even (4, 6, 8)

3 visual steps

Level 25 visual plan for Rules - digit-sum (3, 9)

Level 25 / mastery

Rules - digit-sum (3, 9)

3 visual steps

Level 26 visual plan for Rule for 7

Level 26 / mastery

Rule for 7

3 visual steps

Level 27 visual plan for Rule for 11

Level 27 / mastery

Rule for 11

3 visual steps

Level 28 visual plan for Rule for 12

Level 28 / realistic untimed

Rule for 12

3 visual steps

Level 29 visual plan for Rules - all (small N)

Level 29 / mastery

Rules - all (small N)

3 visual steps

Level 30 visual plan for Rules mastery (4-digit N)

Level 30 / mastery

Rules mastery (4-digit N)

3 visual steps

Practice this category

Use the method on live number theory levels.

Open Number Theory Workouts