Formulas and rules
Every key math formula and rule, organised by topic and school level, with examples and study tips.
Arithmetic 5
M1
Multiplication
a x b = rows x columns
Multiplication is repeated addition, shown as a rectangular grid.
M1
Division
dividend / divisor = quotient
Division shares a total into equal groups. It undoes multiplication.
M1
Divisibility rules
By 2: even last digit. By 3: digit sum divisible by 3. By 5: last digit 0 or 5. By 9: digit sum divisible by 9. By 10: last digit 0.
M1
Factors and multiples
A factor divides a number exactly. A multiple is found by multiplying a number by a whole number.
M1
Prime numbers
A prime has exactly two factors: 1 and itself. Primes start 2, 3, 5, 7, 11, 13...