In an ordinary annuity, when does the interest on a yearly investment start building interest?

The interest on a yearly investment start building interest - at the end of the first period.

Step-by-step explanation:

In an ordinary annuity, the interest on a yearly investment start building interest - at the end of the first period.

An ordinary annuity is a series of payments, where all the payments are of the same amount and are paid at the same intervals of time. The interest is calculated at the end of first period.

at the end of the first period