The sum of 324 and 135 is 503. Which number base was used for this calculation.

Base 6 was used

Step-by-step explanation:

Here, we want to find which number base was used for the addition calculation

We start by adding the two end numbers

4 + 5 = 9

But 3 was recorded;

That means we can have 6 as the number base( 9/6 = 1 r 3)

We still continue to verify this;

The next addition is 2+3 = 5, adding the 1 brought forward, we have 6, but 0 was recorded

6/6 is (1 r 0)

This still further corroborated the earlier assertion;

then lastly 3 + 1 + 1 (1 brought forward); 5

This was recorded directly to show that the base in question is not less than 5

Hence our base of addition is base 6