Question

find the average of 12 numbers if the average of the first nine number is 21 and the average of the last three is 17.​

Answer 1

Answer:

20

Step-by-step explanation

Let sum of first nine numbers be x

Then, x/9 = 21 => x = 189

Now, let sum of last three numbers be y

Then, y/3 = 17 => y = 51

Now, x+y = Sum of 12 numbers, say z

=> 189 + 51 = z => z = 240

Now, average of 12 numbers, z/12 = 240/12 = 20

Hence, the average of 12 numbers is 20

Answer 2

Answer:

20

Step-by-step explanation:

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