Question

the average of 12 number is 15. If a number 41 is included then the average of 13 number is

Answer 1

sum of observation is 12×15=180
Therefore 41 is added. The sum of new observations is 180+41=221.
The new average is equals to 221/13=17

Answer 2

According to the Question

Sum of 12 numbers

= 12 × 15

= 180

Here adding 41 into these numbers

Sum of 13 numbers :-

= 180 + 41

= 221

Now :-

Average of 13 numbers

${\implies\dfrac{221}{13}}$

= 17