Answer: One third plus one third is two-thirds.

To calculate the sum of one third plus one third, we first need to ensure that the fractions have the same denominator. In this case, both fractions already have the same denominator, which is 3.

Then, we simply add the numerators (the top numbers of the fractions) together while keeping the denominator the same:

1/3 + 1/3 = (1+1)/3 = 2/3

So, the result of One Third Plus One Third is 2/3.

This calculation demonstrates that when adding fractions with the same denominator, we can simply add their numerators together while keeping the denominator unchanged. This process is straightforward and allows us to find the sum of fractions efficiently.