SOLUTION: A man has $2000 invested at 7% and $5000 at 4% simple interest. What additional sum must he invest at 6% to give him an overall return of 5%?

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Question 667740: A man has $2000 invested at 7% and $5000 at 4% simple interest. What additional sum must he invest at 6% to give him an overall return of 5%?

Answer by mananth(16946)   (Show Source): You can put this solution on YOUR website!
Investment I 7.00% 2000
Investment II 4.00% 5000
Investment III 6.00% x

Total 5.00%
The sum of individual interest earned = 5.00% of Total investment
Total Interest
7.00%*2000+4.00%*5000+6.00%x=5.00%(2000+5000+x)
140+ 200 + 6.00% x = 350 + 5.00% x
6.00% x- 5.00% x= 350 -140 -200
1.00% x= 10
x= 1000
He has to invest $ 1000

CHECK

140 200 60 = 400

Total = 8000
5.00% on 8000 = 400

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