Worked problem pages
Each page explains the idea, then works through real problems from the Mathyessy bank step by step.
Divisibility rules practiceDivisibility rules let you test huge numbers in seconds, and they are the key to missing-digit puzzles.Prime factorization practiceBreaking a number into primes is the first step for divisors, GCD, LCM, perfect squares and factorial problems.Greatest common divisor (GCD) practiceThe GCD is the biggest number that divides both. Prime factorizations and the Euclidean algorithm find it fast.Least common multiple (LCM) practiceTwo bells, two buses, two blinking lights: when do they line up again? That's the LCM.Counting divisors practiceHow many factors does 360 have? You don't need to list them. Factor it into primes and multiply.Modular arithmetic practiceModular arithmetic is arithmetic with remainders. It turns giant calculations into small ones.Units digit and cycles practiceWhat is the last digit of 7²⁰²⁶? Only the last digits matter, and they repeat in short cycles.Number bases practiceBase 10 uses place values 1, 10, 100… Other bases work the same way with different place values.Trailing zeros in factorials practiceEach trailing zero comes from a factor of 10 = 2 × 5. In a factorial, the 5s are the bottleneck.
Every Number Theory practice set in Mathyessy
Each link opens that topic's question set in the free app. Questions get harder as you go, and you get instant feedback after each answer.
- Divisibility Rules · worked problems
- Primes And Primality
- Prime Factorization · worked problems
- Greatest Common Divisor · worked problems
- Least Common Multiple · worked problems
- Divisor Counting · worked problems
- Divisor Sums
- Remainders
- Modular Arithmetic · worked problems
- Units Digits And Cycles · worked problems
- Powers Mod M
- Number Bases · worked problems
- Digit Sums And Digital Roots
- Perfect Squares
- Perfect Cubes
- Trailing Zeros In Factorials · worked problems
- Diophantine Equations Intro
- Chinese Remainder Intro
- Parity And Consecutive Integers
- Exponent Last Digits