SOLUTION: An investor has $10,000 to invest in three types of bonds: short term, medium term and long term bonds. Short term bonds have a return of 4% anually, medium bonds have a return of

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: An investor has $10,000 to invest in three types of bonds: short term, medium term and long term bonds. Short term bonds have a return of 4% anually, medium bonds have a return of       Log On


   



Question 173808: An investor has $10,000 to invest in three types of bonds: short term, medium term and long term bonds. Short term bonds have a return of 4% anually, medium bonds have a return of 5% anually and long term bonds have a return of 6% anually. The investor wants a anual return of 5.1% with equal investments in short and medium term bonds. How much does he have to invest in long term bonds?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let s= amount invested in short-term
Let m= amount invested in medium term
Let l= amount invested in long yerm
Given is:
s+%2B+m+%2B+l+=+10000
s+=+m
.04s= annual return on short-terms
.05m= annual return on medium-terms
.06l= annual return on long-terms
------------------------
The problem is looking for an overall return
of 5.1% on these 3 investments, so, in words
(sum of the returns)/(total investment) = 5.1%
%28.04s+%2B+.05m+%2B+.06l%29+%2F+10000+=+.051
Multiply both sides by 10000
(1) .04s+%2B+.05m+%2B+.06l+=+510
Multiply both sides by 100
(1) 4s+%2B+5m+%2B+6l+=+51000
(2) s+%2B+m+%2B+l+=+10000 (given)
Multiply both sides of (2) by 6
(2) 6s+%2B+6m+%2B+6l+=+60000
Subtract (1) from (2)
2s+%2B+m++=+9000
And, since s+=+m,
2m+%2B+m+=+9000
3m+=+9000
m+=+3000
s+=+3000
s+%2B+m+%2B+l+=+10000
3000+%2B+3000+%2B+l+=+10000
l+=+10000+-+6000
l+=+4000
He has to invest $4000 in long-term bonds
check answer:
%28.04s+%2B+.05m+%2B+.06l%29+%2F+10000+=+.051
%28.04%2A3000+%2B+.05%2A3000+%2B+.06%2A4000%29+%2F+10000+=+.051
%28120+%2B+150+%2B+240%29+%2F+10000+=+.051
510+%2F+10000+=+.051
.051+=+.051
OK