# Glossary

Decomposition of numbers in arithmetic involves breaking down numbers into base-ten components. For example, the number 463 can be broken down into 400 plus 60 plus 3 by decomposing it into hundreds, tens and ones.

Values that summarise a given data set, which can be either a representation of the entire population or a sample of it. Descriptive statistics are broken down into measures of central tendency and measures of variability, or spread.

A diameter is a chord passing through the centre of a circle. The word diameter is also used for the length of the diameter.

Direct comparison is the process of directly aligning the attributes to be compared. For example, the length of two pencils can be compared by placing the pencils side-by-side along their lengths, and using a common starting point or baseline.

Two quantities are in direct proportion if as one increases, the other increases by the same percentage. That is, the two quantities are linked by a constant multiplier.

Separate and distinct items.

Multiplication of numbers is distributive over addition because the product of one number with the sum of two others equals the sum of the products of the first number with each of the others. Algebraically this is a(b+c)=ab+ac.

This means that we can multiply two numbers by expressing one (or both) as a sum and then multiplying each part of the sum by the other number (or each part of its sum.)

For example, 8 x 17 = 8 x (10 + 7) = 8 x 10 + 8 x 7 = 80 + 56 = 136.