SOLUTION: Bernadette inherited $15,000 and invested it in two municipal bonds, which pay 7 percent and 9 percent simple interest. the annual interest is $1230. Find the amount at each rate

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Question 520137: Bernadette inherited $15,000 and invested it in two municipal bonds, which pay 7 percent and 9 percent simple interest. the annual interest is $1230. Find the amount at each rate.
Answer by Maths68(1474) About Me  (Show Source):
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Let
Amount invested at 7% = x
Amount invested at 9% = 15000-x
Given
Total interest on both investments = 1230

7% * (x) + 9% * (15000-x) = 1230
7/100 * x + 9/100 * (15000-x) = 1230
Multiply by 100 both sides
7*x + 9 * (15000-x) = 1230 * 100
7x+ 135000-9x = 123000
7x-9x = 123000-135000
-2x=-12000
-2x/-2=-12000/-2
x=6000

Amount invested at 7% = x = 6000
Amount invested at 9% = 15000-x = 15000 - 6000 = 9000
Check
=====
6000 * 7/100 + 9000 * 9/100 = 1230
60*7 + 90*9 = 1230
420 + 810 = 1230
1230=1230