SOLUTION: Two investments were made totaling $10,500. Part of the $10,500 was invested at 9% and the remaining amount was invested at 12%. The annual interest from both investments was $1,14

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Question 677729: Two investments were made totaling $10,500. Part of the $10,500 was invested at 9% and the remaining amount was invested at 12%. The annual interest from both investments was $1,140. How much was invested at each rate?
Answer by partha_ban(41) About Me  (Show Source):
You can put this solution on YOUR website!
Let, x be the amount invested at 9% interest.
(10500 - x) be the amount invested at 12% interest.
From I = Prt, interest from first investment = x+%2A+%289%2F100%29+%2A+1
= 9x%2F100
Interest from 2nd investment = %2810500-x%29+%2A+%2812%2F100%29+%2A+1
= %2812%2A%2810500-x%29%29%2F100
By condition, 9x%2F100+%2B+%2812%2A%2810500-x%29%29%2F100+=+1140
%289x+%2B+126000+-+12x%29%2F100+=+1140
9x + 126000 - 12x = 1140 * 100
9x - 12 x = 114000 - 126000
-3x = -12000
x+=+%28-12000%29%2F%28-3%29
x = 4000
Therefore, $4,000 has been invested at 9% interest.
$(10,500 - 4,000) = $6,500 has been invested at 12% interest.