Question 52990This question is from textbook Intoductory Algebra
: Frank has half of his investments in stock paying an 11% dividend and the other half in a debentured stock paying 13% interest. If his total annual interest is $840, how much does he have invested.
Find the equation(s) and solve using substitution or elimination.
This question is from textbook Intoductory Algebra
Answer by funmath(2933)   (Show Source):
You can put this solution on YOUR website! Let the amount he invested at 11%=x
Let the amount he invested at 13%=y
He invested the same amount in both stocks, so x=y
Interest(i)=principle(p)*rate(r)*time(t), but unless they specify that the time is different than one, i=p*r.
So the amount of interest he gets at 11%=.11x
The amount of interest he gets at 13%=.13y
Add the two together and your interest is=840
Therefore your system of linear equations is:
x=y
.11x+.13y=840
----------------Substitute the first equation into the second and you have:
.11x+.13(x)=840
.24x=840
.24x/.24=840/.24
x=$3,500 (the amount he invested at 11%)
y=x so y=$3,500 (the amount he invested at 13%)
Add the two investments together to find out how much he invested all together:
$3,500+$3,500=$7,000 is the amount he has invested altogether.
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