Can you calculate average by adding one number

Question

This ia mathematical question but I like to do it in code.
Values : 4,8,12
The first average of 4 and 8 is 6
If I have a new number say 12
Do I really need to calculate a new total and divide that by 3. Or is there a smart way, which result in a correct average ?

Answer 1

If you only add one element and x denotes the new amount of elements, the new average would equal
( x - 1 / x ) * oldAverage + ( 1 / x ) * newElement
Not sure if that is better though. Maybe someone else can provide an even smarter method.

Answer 2

If you use the formula that Shadow mentioned, make sure you use floating point division.

Answer 3

Yes! You can write a while loop that takes input and appends it to the array, then print the array sum divided by the array length. Putting it inside a while loop would allow you to keep adding elements to the array.

Answer 4

Shadow nailed it and I believe that's the straightforward way by reversing the computed average and I would like to add some explanation on top of it.

Basically what the formula does is:-

✔ Obtain the sum of original number list by multiplying original average with its size

✔ Add the new number in and finally divide by the new size

That's the reason we have both addend sharing the same denominator. 😉

Answer 5

I managed to implement it in code
And it does work.

Thank you.

https://code.sololearn.com/cbWtOagXA65L