Question

$5,000 is invested at 3% interest. How much money must be invested at 5% interest so that the total interest from the two investments is $275 after one year?

Answer 1

$Part \ of\ 5000\ should\ be\ invested\ at\ 3\%\ and\ part\ at\ 5\%.\\\\ x-\ part\ of\ 5000\ invested\ at \3\%\\x*3\%+(5000-x)*5\%=275\\ 0,03x+0,05(5000-x)=275\\ 0,03x+0,05*5000-0,05x=275\\ -0,02x=275-250\\ -0,02x=-25\ |:-0,2\\\ x=125\\ 5000-125=4875\\ 125 \ \ should\ be\ at\ 3\%\ and\ 4875\ at \ 5\%.$