Question 1020441
 Christin Demin invested part of her P240,000 in a firm that pays 12% per annum while the rest in a company that pays 7% per annum. If by the end of a year the two investments yielded a total interest of P21,600 how much was invested at each rate? 
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Equations:
Quantity:: t+s = 240,000
Interest::12t+7s = 2160000
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Modify for elimination::
7t + 7s = 7*240000
12t + 7s = 2160000
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Subtract and solve for "t"::
5t = 480000
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t = 96000 (amt. invested at 12%)
s = 240000-96000 = 144000 (amt invested at 7%)
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Cheers,
Stan H.
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