# should I use the mean or weighted mean in this example?

An investor calculated the percentages of each of three stock investments with payoffs as shown. Find the average payoff for the three stock investments. what should I use in this case to calculate the average?

If you know how much money is invested in each of the three investments, it makes sense to do a weighted average, with the weights coming from $$\frac{A_i}{A}$$, where $$A_i$$ is the amount of money invested in investment $$i$$, and $$A$$ is the total money invested, so that $$A = A_1 + A_2 + A_3$$
Otherwise you could do a simple equally weighted average (i.e. average payoff = $$\frac{1}{3}(p_1 + p_2 + p_3)$$, where $$p_i$$ is the payoff for investment $$i$$.