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If the ratio of one length to another is 1 : 2, this means that the second length is twice as large as the first. If a boy has 5 sweets and a girl has 3, the ratio of the boy’s sweets to the girl’s sweets is 5 : 3 .


A percentage is a fraction whose denominator is 100 (the numerator of a fraction is the top term, the denominator is the bottom term).

Directed Numbers

Numbers can either be positive or negative. Often brackets are put around negative numbers to make them easier to read, e.g. (-2). If a number is positive, the + is usually missed out before the number.