M1 - Explorer

Multiplication

a x b = rows x columns

Multiplication is repeated addition, shown as a rectangular grid.

Division

dividend / divisor = quotient

Division shares a total into equal groups. It undoes multiplication.

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.

Factors and multiples

A factor divides a number exactly. A multiple is found by multiplying a number by a whole number.

Prime numbers

A prime has exactly two factors: 1 and itself. Primes start 2, 3, 5, 7, 11, 13...

What is a fraction

numerator / denominator

A fraction is equal parts of a whole. The denominator is the number of parts, the numerator the number taken.

Equivalent fractions

a/b = (a x k)/(b x k)

Multiplying or dividing top and bottom by the same number keeps the value.

Comparing fractions

With the same denominator, the larger numerator is bigger. With the same numerator, the smaller denominator is bigger.