__What is Average__

An average or more accurately an arithmetic mean is, in crude terms, the sum of n different data divided by n.

Averages of a group is defined as the ratio of sum of all the items in the group to the number of items in the group.

**Average = (Sum of all items in the group)/ Number of items in the group**

Now, sum of all items can be ‘the sum of number of quantities like apple, people etc’ or ‘sum of values of the item like 10 coins of 2Rs each etc’.

**Some Important Concepts:**

**1. **Average =total of data/No.of data

**2. **If the value of each item is increase by the same value a, then the average of the group or items will also increase by a.

**3. **If the value of each item is decreased by the same value a, then the average of the group of items will also decrease by a.

**4. **If the value of each item is multiplied by the same value a, then the average of the group or items will also get multiplied by a.

**5. **If the value of each item is multiplied by the same value a, then the average of the group or items will also get divided by a.

**6. **If we know only the average of the two groups individually, we cannot find out the average of the combined group of items.

**7.Average of n natural no's=(n+1)/2**

**8.Average of even No'=(n+1)**

**9.Average of odd No'= n**

**10.General Formula=(1st number +Last number)/2**