It's wrong. 1/3 + (1/3 * 1/3) = 3/9 + 1/9 = 4/9. It's close though.
However, one third plus one half of a third is correct. 1/3 + (1/2 * 1/3) = 1/3 + (1.5/3 * 1/3) = 1/3 + 0.5/3 = 1.5/3 = 1/2
It's wrong. 1/3 + (1/3 * 1/3) = 3/9 + 1/9 = 4/9. It's close though.
However, one third plus one half of a third is correct. 1/3 + (1/2 * 1/3) = 1/3 + (1.5/3 * 1/3) = 1/3 + 0.5/3 = 1.5/3 = 1/2