In mathematical notation, ∑ means summation. So wherever you see the symbol, you have to sum over all elements in the set. Let's solve the question.
a. ∑m means, to sum all elements in the set m: ∑m = 12 + 15 + 20 + 30 = 77
b. ∑[tex]f^{2}[/tex] means to sum all elements in the set f as the square of the elements f = [tex]5^{2} + 9^{2} + 10^{2} + 16^{2} = 25 + 81 + 100 + 256 = 462[/tex]
c. ∑mf means to sum all elements as the product of the elements of m and f = (12×5) + (15×9) + (20[tex](12^{2}(5)) + (15^{2}(9)) + (20^{2}(10)) + (30^{2}(16)) = 21145[/tex]10) + (30×16) = 875
d. ∑[tex]m^{2}f[/tex] means to sum all elements as the product of the square of m and f = [tex]((12*12)(5)) + ((15*15)(9)) + ((20*20)(10)) + ((30*30)(16)) = 21145[/tex]
