Explanation : The total return of an index is the price appreciation, or change in the
value of the price return index, plus income (dividends and/or interest)
over the period, expressed as a percentage of the beginning value of the
price return index.
Return of A: (15 − 20 + 2)/20 = −15%
Return of B: (48 − 40 + 4)/40 = 30%
Return of C: (60 − 60 + 9)/60 = 15%
An equal-weighted index applies equal weight to each security‟s return;
therefore, the total return = 1/3 ∗ (−15% + 30% + 15%) = 10%.