Question

In planning her retirement, Liza deposits some money at 2.5% interest, with twice as much deposited at 4.5%. Find the amount deposited at each rate if the total annual interest income is $1150.

Answer 1

Let us assume $x is deposit at 2.5% interest.

At the rate 4.5% deposited amount is twice of the amount deposited at 2.5%.

Therefore, at the rate 4.5% deposited amount = $2x.

Total interest earned by both different deposited amount at the rate 2.5% and at the rate 4.5% = $1150.

We can setup an eqation now,

Interest earned on $x at 2.5% + interest earned on $2 at 4.5% = $1150.

2.5% of x + 4.5% of 2x = 1150

Percentage could be written in decimals by dividing by 100.

Therefore, 2.5% = 2.5 /100= 0.025 and 4.5% = 4.5/100 = 0.045.

We could rewrite above equation as,

0.025*x + 0.045 * 2x = 1150

0.025x + 0.09x =1150

Adding 0.025x + 0.09x, we get 0.115x.

So, 0.115x=1150.

Dividing both sides by 0.115.

0.115x/0.115=1150/0.115.

x= $1000.

2x= 2* 1000= $2000

Therefore,

$1000 deposited at 2.5% and $2000 deposited at 4.5%.