Question 270651
x = Amount of money invested at 4%
y = Amount of money invested at 7%


Combined Interest = 1300


Combined Interest Equation equals:


.04*x + .07*y = 1300


Total invested = 25,000


Total Investment Equation equals:


x + y = 25000


You need to solve these two equations simultaneously to get your answer.


The equations are:


x + y = 25000
.04x + .07y = 1300


use the first equation to solve for y in terms of x.


you get:


y = 25000 - x


substitute for y in the second equation to get:


.04x + .07(25000-x) = 1300


simplify to get:


.04x + .07*25000 - .07*x = 1300


simplify further to get:


.04x + 1750 - .07x = 1300


combine like terms to get:


-.03x + 1750 = 1300


subtract 1750 from both sides of equation to get:


-.03x = 1300 - 1750 = -450


divide both sides of equation by -.03 to get:


x = -450/-.03 = 150000


since x + y = 2500, then y = 10000


your answer should be:


Amount invested at 4% = 15000.


Amount invested at 7% = 10000.


Interest on 15000 at 4% = .04 * 15000 = 600.


Interest on 10000 at 7% = .07 * 10000 = 700.


Combined interest = 600 + 700 = 1300, confirming the answer is good.