The number of observations in a group is 40. If the average of first 10 observations is 4.5 and the next 30 observations is 3. Find the average of whole group.

To find the average of the whole group, we need to find the total sum of all observations and then divide it by the total number of observations.

Step 1: Find the sum of the first 10 observations The average of the first 10 observations is 4.5, so the total sum of these observations is 4.5 * 10 = 45.

Step 2: Find the sum of the next 30 observations The average of the next 30 observations is 3, so the total sum of these observations is 3 * 30 = 90.

Step 3: Find the total sum of all observations The total sum of all observations is the sum of the first 10 observations and the next 30 observations, which is 45 + 90 = 135.

Step 4: Find the total number of observations The total number of observations is 40.

Step 5: Find the average of the whole group The average of the whole group is the total sum of all observations divided by the total number of observations, which is 135 / 40 = 3.375.

So, the average of the whole group is 3.375.