Answer: $7800 was invested at 9%
$5900 was invested at 3%
Explanation:
Let x represent the amount invested in the fund that paid a dividend of 9%.
Let y represent the amount invested in the fund that paid a dividend of 3%.
Last year, the first fund paid a dividend of 9% and the second a dividend of 3%, and you received a total of $879. This means that
0.09x + 0.03y = 879- - - - - - - - - 1
This year, the first fund paid a 10% dividend and the second only 1%, and you received a total of $839. It means that
0.1x + 0.01y = 839 - - - - - - - - - -2
Multiplying equation 1 by 0.1 and equation 2 by 0.09, it becomes
0.009x + 0.003y = 87.9
0.009x + 0.0009y = 75.51
Subtracting, it becomes
0.0021y = 12.39
y = 12.39/0.0021
y = 5900
Substituting y = 5900 into equation 1, it becomes
0.09x + 0.03 × 5900 = 879
0.09x + 177 = 879
0.09x = 879 - 177
0.09x = 702
x = 702/0.09
x = 7800