Question

Brian has money in two savings accounts. One rate is 5% and the other is 10%. If he has $900 more in the 10% account and the total interest is $273, how much is invested in each savings account?

Answer 1

Answers:

1220 dollars invested at 5% interest rate.

2120 dollars invested at 10% interest rate.

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Step-by-step explanation:

Label the two accounts A and B.

Account A earns 5% interest

Account B earns 10% interest

Brian invests x dollars in account A and x+900 dollars in account B.

Using the formula, i = P*r*t, we can compute the simple interest for both accounts

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Start with account A over the course of t = 1 year.

i = P*r*t

i = x*0.05*1

i = 0.05x

then compute the interest for account B (use t = 1 also).

i = P*r*t

i = (x+900)*0.10*1

i = 0.10x + 90

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Over the course of 1 year, Brian earns 0.05x dollars in interest with account A and also 0.10x+90 dollars in interest with account B.

In total he earns 0.05x+0.10x+90 = 0.15x+90 dollars in interest.

We're told this amount of interest he earns is $273, so,

0.15x+90 = 273

0.15x+90-90 = 273-90

0.15x = 183

0.15x/0.15 = 183/0.15

x = 1220

This means $1220 was invested at 5% interest.

x+900 = 1220+900 = 2120

and $2120 was invested at 10% interest.

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Check:

If you invested $1220 in account A, then you earn

i = P*r*t

i = 1220*0.05*1

i = 61 dollars in interest

If you invest $2120 in account B, then you earn

i = P*r*t

i = 2120*0.10*1

i = 212 dollars in interest

So you get a total of 61+212 = 273 dollars in interest from both accounts. This confirms the two answers.