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Question 1045551:  Betsy, a recent retiree, requires $6,000 per year in extra income.  She has $50,000 to invest and can invest in B-rated bonds paying 13% per year or in a certificate of deposit (CD) paying 3% per year.  How much money should be invested in each to realize exactly $6,000 in interest per year? 
 Answer by Theo(13342)      (Show Source): 
You can  put this solution on YOUR website! let x = the amount invested in b rated bonds. 
let y = the amount invested in certificates of deposit.
 
 
x + y = 50000
 
 
this means that the total investment must be equal to 50,000 dollars.
 
 
.13x + .03y = 6000
 
 
this means that the total interest must be equal to 6,000 dollars.
 
 
these are 2 equations that need to be solved simultaneously.
 
 
i will solve by elimination.
 
 
start with:
 
 
x + y = 50000 (first equation) 
.13x + .03y = 6000 (second eauation)
 
 
multiply both sides of the first equation by 13 and multiply both sides of the second equation by 100 to get:
 
 
13x + 13y = 650000 
13x + 3y = 600000
 
 
subtract the second equation from the first to get 10y = 50000.
 
 
divide both sides of that equation by 10 to get y = 5000
 
 
since x + y = 50000, then x must be equal to 45000.
 
 
your solution should be that 45000 must be invested at 13% and 5000 must be invested at 3%.
 
 
.13 * 45000 + .03 * 5000 = 6000.
 
 
the solution looks good.
 
 
 
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