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RATIO & PROPORTION, PERCENTAGE & AVERAGES

RATIO & PROPORTION, PERCENTAGE & AVERAGES

 

Ratio & Proportion

A proportion is a name we give to a statement that two ratios are equal. It can be written in two ways:

  • two equal fractions,

ab

or

  • using a colon,    a:b = c:d

When two ratios are equal, then the cross products of the ratios are equal.

That is, for the proportion, a:b = c:d ,  a x d = b x 

Percent:

Percent to fraction: x% = x/100

Percentage formula: Rate/100 = Percentage/base

Rate: The percent.
Base: The amount you are taking the percent of.
Percentage: The answer obtained by multiplying the base by the rate

Average:

Let a1,a2,a3,……,an be a set of numbers, average = (a1 + a2 + a3,+……+ an)/n