Simple Interest for 9th grade Pre-Algebra

[krankypoptart]

Michelle invested $10,000 for one year, part at 8% interest and the rest at 12% annual interest. Her total interest for the year was $944. How much money did she invest at 12% interest?

 

[Deleted member 4993]

Michelle invested $10,000 for one year, part at 8% interest and the rest at 12% annual interest. Her total interest for the year was $944. How much money did she invest at 12% interest?

To start with:

Name variables:

Let

amount invested at 8% interest = E ? (1)what will be the interest on E?
amount invested at 12% interest = T ? (2)what will be the interest on T?

You know then

E + T = 10,000

E = 10000 - T

and so on......

Please show us your work, indicating exactly where you are stuck - so that we know where to begin to help you.

 

[krankypoptart]

Michelle invested $10,000 for one year, part at 8% interest and the rest at 12% annual interest. Her total interest for the year was $944. How much money did she invest at 12% interest?

To start with:

Name variables:

Let

amount invested at 8% interest = E ? (1)what will be the interest on E?
amount invested at 12% interest = T ? (2)what will be the interest on T?

You know then

E + T = 10,000

E = 10000 - T

and so on......

Please show us your work, indicating exactly where you are stuck - so that we know where to begin to help you.

I = prt
944 = 10,000 * .08 * 1

= 800

E + T = 10000
10000 - 800 = 9200
T = 9200

 

[Denis]

944 = 10,000 * .08 * 1
= 800

Well, if you're saying it's possible for 944 to equal 800,
looks like only your teacher can help you.

 

[Deleted member 4993]

[
E + T = 10,000

E = 10000 - T

and so on......

Please show us your work, indicating exactly where you are stuck - so that we know where to begin to help you.

I = prt
944 = 10,000 * .08 * 1 = 800<<< What are you doing here? How can you have 944 = 800???

E + T = 10000
10000 - 800 = 9200<<< What are you doing here? Where did 'E' & 'T' go - where did 800 come from?

Where are the equations (1) and (2) that I had suggested?


T = 9200

 

[krankypoptart]

[quote="Subhotosh Khan":zhui3t6b][
E + T = 10,000

E = 10000 - T

and so on......

Please show us your work, indicating exactly where you are stuck - so that we know where to begin to help you.

[/quote:zhui3t6b]

I = prt
944 = 10,000 * .08 * 1 = 800<<< What are you doing here? How can you have 944 = 800???
Here I plugged in the formula for simple interest. Was I not supposed to do that??
E + T = 10000
10000 - 800 = 9200<<< What are you doing here? Where did 'E' & 'T' go - where did 800 come from?
800 is 8 % of 10,000.
Where are the equations (1) and (2) that I had suggested?
E is the 800 bing subtracted from 10,000. Like you asked in the first two equations. When you said "and so on..." I thought that meant for me to plug in the formula and work from their. I don't really know what to do.

 

[krankypoptart]

quote="Subhotosh Khan"][
E + T = 10,000

E = 10000 - T

and so on......

Please show us your work, indicating exactly where you are stuck - so that we know where to begin to help you.

[/quote]

E + T = 10,000

E= 10000 - T

8 % 0f 10000 = 800 ( Is this following your equation, better???)

10,000 - 800 = 9200
9200 @ 12% = 1104
9200 - 1104
E = 8096

 

[Denis]

Relax, Kranky!

Let's make up another (similar) case:
$6000 is invested at 5%: interest is 6000 * .05 = $300 ; ok?
$4000 is invested at 7%: interest is 4000 * .07 = $280 ; ok?
IF that was the case, then problem would be worded this way:
"Michelle invested $10,000 for one year, part at 5% interest and the rest at 7% annual interest.
Her total interest for the year was $580. How much money did she invest at 7% interest?"

So if A = amount invested at 7%, then 10000 - A = amount invested at 5%
Interest on A = .07(A)
Interest on 10000-A = .05(10000 - A)
Since the total interest = 580, then:
.07A + .05(10000 - A) = 580
Solving:
.07A + 500 - .05A = 580
.02A = 80
A = 80 / .02 = 4000 = amount invested at 7%

Now go do yours the same way...

 

[krankypoptart]

Relax, Kranky!

Let's make up another (similar) case:
$6000 is invested at 5%: interest is 6000 * .05 = $300 ; ok?
$4000 is invested at 7%: interest is 4000 * .07 = $280 ; ok?
IF that was the case, then problem would be worded this way:
"Michelle invested $10,000 for one year, part at 5% interest and the rest at 7% annual interest.
Her total interest for the year was $580. How much money did she invest at 7% interest?"

So if A = amount invested at 7%, then 10000 - A = amount invested at 5%
Interest on A = .07(A)
Interest on 10000-A = .05(10000 - A)
Since the total interest = 580, then:
.07A + .05(10000 - A) = 580
Solving:
.07A + 500 - .05A = 580
.02A = 80
A = 80 / .02 = 4000 = amount invested at 7%

Now go do yours the same way...

I understand!!! Thank you.