Question 706791: suppose 20,000 is invested at 5 % . How much additional money must be invested at 4 % to produce a yield of 4.8 % on the entire amount invested?
Answer by jim_thompson5910(35256)   (Show Source):
You can put this solution on YOUR website! 20,000 is invested at 5 %, so in one year, you will earn 20000*0.05 = 1000 dollars in interest
1000 dollars is 5% of the total amount invested, but we want a 4.8% yield.
Investing an additional x dollars at 4% yields 0.04x dollars after one year.
You have invested 20000 + x dollars total
You earn 1000 + 0.04x dollars in interest alone.
The ratio of interest earned to amount invested is: (1000 + 0.04x)/(20000 + x)
This ratio must be equal to 0.048 (the decimal equivalent of 4.8%) since this is your requirement
So we can say
(1000 + 0.04x)/(20000 + x) = 0.048
I'll let you solve for x.
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