Question

Question #b72fe

Answer 1

I got: `6000 and 4000` Euros

Explanation:

Let us call the two quantities (at `8% and 9%`) `x and y`, we get:

`x+y=10000`
`0.08x+0.09y=840`

Let us solve using the first equation rearranged:

`x=10000-y`

into the second:

`0.08(10000-y)+0.09y=840`

`800-0.08y+0.09y=840`

`0.01y=40`

`y=40/0.01=4000` Euros

so that:

`x=10000-4000=6000` Euros

Answer 2

Elimination Method: `y=4000` euros

Explanation:

Another way to attack it. Using Gio's equations:

`x+y=10000`
`0.08x+0.09y=840`

Since we are looking for `y` which is how much was invested at `9`%, let's eliminate `x`.

We can do that by multiplying the top equation by `0.08` and then subtracting the two equations:

`0.08x+0.08y=800`
`0.08x+0.09y=840`

`-0.01y=-40`

`y=4000` euros