Question

When the mean of 9 numbers were calculated, a score 12 was mistakenly taken as 21. the mean obtained was 19. what will be mean when the actual number 12 is used?

Answer 1

Hello Dear!!!

here's your answer...

The actual mean is 18.

refer the attachment...

Answer 2

Heya

Mean of 9 numbers = 19

=> Sum of the numbers = ( 19 )( 9 )

Now, We correct the scores by subtracting 21 and adding 12.

The correct sum of 9 numbers :
$(19)(9) - 21 + 12$

$= 171 - 21 + 12 = 162$

Hence, when the actual number 12 is used, the mean changes to :
$162 \div 9 = 18$

Hence, the correct Mean is 18