00:01
We're going to use a system of linear equations to solve this problem where $23 ,000 was invested in two bonds, one earning 4 % simple interest and the other 2 % simple interest, and if the investor earns $710 in annual interest, how much was invested in each account.
00:24
So what we're going to do is assign variables, x and a y.
00:27
So we'll have x be the amount invested at 4%, and y will be the amount invested at 2%.
00:39
Since there's a total of $23 ,000 invested, we have the amount invested at 4%, and we add the amount invested at 2%, and that's the $23 ,000.
00:53
And then the amount of interest earned.
00:56
Well, the x amount earned at 4%, so 0 .04 times x plus y is the amount that earned 2%.
01:10
So that's 0 .02y, and that's going to give us the $710 an interest that's earned altogether.
01:22
So there is our system of equations.
01:24
Now we just need to solve that.
01:27
So the bottom equation, if i multiply by 100, that's going to get rid of all the decimals.
01:36
And you can see this is going to become 4x plus 2y...