Question

Find the average of 12 numbers if the average of the first 8 numbers is 21 and the average of the last four numbers is 18.​

Answer 1

Answer:

see below

Step-by-step explanation:

Average of first 8 number = 21

Average of last 4 number = 18

If average of all 12 numbers is 18, then we have 8 x 3 = 24 extra from first eight numbers.

This extra is distributed over all 12 numbers increasing their average by 24/12 = 2.

=> Final average = 18 + 2 = 20