Question

Mr. Smith invest a certain amount of money at 8% interest and twice as much at 5% his annual income from the two Investments is $720 how much does he have invested at 5% in dollars

Answer 1

Answer: he invested $8000 at 5%

Step-by-step explanation:

Let x represent the amount which he invested in the account paying 8% interest.

Let y represent the amount which he invested in the account paying 5% interest.

Mr. Smith invest a certain amount of money at 8% interest and twice as much at 5% . This means that

xmy = 2x

The formula for determining simple interest is expressed as

I = PRT/100

Considering the account paying 8% interest,

P = $x

T = 1 year

R = 8℅

I = (x × 8 × 1)/100 = 0.08x

Considering the account paying 5% interest,

P = $y

T = 1 year

R = 5℅

I = (y × 6 × 1)/100 = 0.05y

His annual income from the two Investments is $720 it means that

0.08x + 0.05y = 720 - - - - - - - - - -1

Substituting y = 2x into equation 1, it becomes

0.08x + 0.05 × 2x = 720

0.08x + 0.1x = 720

0.18x = 720

x = 720/0.18

x = 4000

y = 2x = 2 × 4000

y = $8000