Question

John invest $5,000 in one account and $8,000 in an account paying 4% more in interest. He earned $1,230 in interest after one year. At what rates did he invest​

Answer 1

Given:

John invest $5,000 in one account and $8,000 in an account paying 4% more in interest.

Total interest in one year = $1230

To find:

The rates of the investments.

Solution:

Let x% be the rate of interest on investment $5000.

Then, (x+4)% is the rate of interest on investment $8000.

Total interest is $1230. So,

`5000* (x)/(100)+8000* (x+4)/(100)=1230`

`50x+80(x+4)=1230`

`50x+80x+320=1230`

`130x=1230-320`

`130x=910`

Divide both sides by 130.

`x=(910)/(130)`

`x=7`

Now,

`x\%=7\%`

`(x+4)\%=(7+4)\%=11\%`

Therefore, $5,000 is invested at 7% and $8,000 is invested at 11%.