Average is the sum of quantities divided by the number of those quantities. It is dividing the total equally for all.

Average = Sum of items /Number of items

Average lies between the least term and the highest term .

If each term is increased by 'K', then the average gets increased by 'K' (Same condition holds true for decreased, multiplied and divided)

For a number series with equal difference, the Average is the mean of first and last (or) the middle term if exists.

Average = F+L /2

Counting principle:

The number of times a quantity with a certain price is counted, those many times we need to multiply the price to get the total value.

Mixtures:

When two quantities with different prices are mixed, we get a quantity with a price which lies between the prices of two quantities mixed.

By using Allegation rule, we can find out the ratio in which a cheaper price quantity is mixed with a higher price quantity to get a desired price quantity.

Quantity of cheaper price / Quantity of Higher price = Higher price -Mean price /Mean price-cheaper price