SOLUTION: please help me solve and explain this word problem: An investment club invested part of $8000 at 10% annual interest and the rest at 12%. If the annual income from these investmen

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Question 902343: please help me solve and explain this word problem:
An investment club invested part of $8000 at 10% annual interest and the rest at 12%. If the annual income from these investments is $900, how much was invested at each rate?
I understood to have "let" statements. So my "let" statements are: let x=10% annual interest and let Y=12% annual interest. I know to find two equations; how much is invested but I don't know the other one.
Thank you for reading and trying to answer my questions.

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
please help me solve and explain this word problem:
An investment club invested part of $8000 at 10% annual interest and the rest at 12%. If the annual income from these investments is $900, how much was invested at each rate?
I understood to have "let" statements. So my "let" statements are: let x=10% annual interest and let Y=12% annual interest. I know to find two equations; how much is invested but I don't know the other one.
Thank you for reading and trying to answer my questions.
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Let

x = amount (in dollars) invested at 10%
y = amount (in dollars) invested at 12%

You can only pick one account or the other. Because you have $8000 total to invest, which is broken up, you will have this equation

x%2By+=+8000

That means that the sum of the two pieces must add back up to $8,000.


Solve for y:

x%2By+=+8000

x%2By-x+=+8000-x

y%2Bx-x+=+8000-x

y%2B0x+=+8000-x

y%2B0+=+8000-x

y+=+8000-x

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If you invest x dollars at 10% simple annual interest, then you earn 0.10x dollars in interest alone just from that investment.

Similarly, if you invest y dollars at 12% simple annual interest, then you earn 0.12y dollars.

Combined you earn 0.10x+%2B+0.12y dollars annually in just interest.

We are told that "the annual income from these investments is $900" therefore

0.10x+%2B+0.12y+=+900

--------------------------

0.10x+%2B+0.12y+=+900

0.10x+%2B+0.12%28y%29+=+900

0.10x+%2B+0.12%288000+-+x%29+=+900 Replace every copy of 'y' with '8000-x' (this works because y+=+8000-x)

Now we solve for x

0.10x+%2B+0.12%288000%29+%2B+0.12%28-x%29+=+900

0.10x+%2B+960+-+0.12x+=+900

0.10x+-+0.12x+%2B+960+=+900

-0.02x+%2B+960+=+900

-0.02x+%2B+960-960+=+900-960

-0.02x+%2B+0+=+-60

-0.02x+=+-60

x+=+%28-60%29%2F%28-0.02%29

x+=+3000

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Then we use this value of x to find y

y+=+8000-x

y+=+8000-3000

y+=+5000

----------------------

Summary:

$3,000 was invested at 10%
$5,000 was invested at 12%


Note: if you are unsure of what x+=+3000 and y+=+5000 mean together in the real world, look back up at the "let" statements.