Section 3.4 Applications of Systems of Linear Equations in Two Variables 263 3. Applications Involving Principal and Interest Solving an Application Involving Finance Example 3 Serena invested money in two mutual funds. One had a return of 4.5% and the other had a return of 7%. Twice as much was invested at 7% as at 4.5%. If the amount earned on the original principal at the end of 1 yr was $1017.50, determine the amount invested in each fund. Solution: Let x represent the amount invested at 4.5%. Let y represent the amount invested at 7%. 4.5% Account 7% Account Total Principal x y Amount earned 0.045x 0.07y 1017.50 Because the amount invested at 7% was twice the amount invested at 4.5%,we have °Amount invested at 7% ¢ 2 ° amount invested at 4.5% From the second row of the table, we have ¢ ° total ¢ y 2x amount earned ¢ 0.045x 0.07y 1017.50 Multiply by 1000 to clear decimals. Because the y variable in the first equation is isolated, we will use the substitution method. Substitute the quantity 2x into the second equation. Solve for x. ¢ ° amount earned from 7% account y 2x ° Amount earned from 4.5% account 45x 70y 1,017,500 45x 7012x2 1,017,500 45x 140x 1,017,500 y 2x 185x 1,017,500 x 1,017,500 185 x 5500 y 2155002 x 5500 y 2x Substitute into the equation to solve for y. y 11,000 x 5500, Because the amount invested at 4.5% was $5500. Because y 11,000, the amount invested at 7% was $11,000. Skill Practice 3. Seth invested money in two accounts, one paying 5% interest and the other paying 6% interest.The amount invested at 6% was $1000 more than the amount invested at 5%. He earned a total of $830 interest in 1 yr. Use a system of equations to find the amount invested in each account. Answer 3. Seth invested $7000 at 5% and $8000 at 6%.
miller_intermediate_algebra_4e_ch1_3
To see the actual publication please follow the link above