Question

The average of a list of 4 numbers is 20. If the number 10 is inserted in the list, what will be the average of

the new list of 5 numbers?

Answer 1

Answer: 18

Explanation:

To calculate an average, you sum up all of the numbers and divide by the number of numbers. Since the average of a list of 4 numbers is 20, if we multiply 20 by 4 we have the sum of those four numbers, which is 80.

Now, if we want to add 10 into the list, we have 80 + 10 = 90 to add it into the sum of all of the numbers. We have 5 numbers now, so to find the average we do 90 / 5 = 18.