SOLUTION: Could you guide me about the following problem?Tanks.. N.has invested a total of $8000, some at 4% and the rest at 7%. If the 4% invenstment yields $155 more than the 7% invenstme

Question 202008: Could you guide me about the following problem?Tanks..
N.has invested a total of $8000, some at 4% and the rest at 7%. If the 4% invenstment yields $155 more than the 7% invenstment, how much was invested at 4%?
I've written: 8000=2x+155 . Is it correct or I must use of either 4% and 7%?
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
Let

x = amount invested at 4%
y = amount invested at 7%

"N.has invested a total of $8000" means that . Solving for "y" gets us

Since "the 4% investment yields $155 more than the 7% investment", we know that

Now multiply EVERY term by 100 to get

Now plug in

Distribute.

Combine like terms on the right side.

Add to both sides.

Combine like terms on the left side.

Divide both sides by to isolate .

Reduce.

Go back to the previously isolated equation

Plug in

Add

===============================================================

Answer:

So the solutions are and

This means that $6,500 was invested at 4% while $1,500 was invested at 7%
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