Question 1203494
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After a Merchant has invested 4,500 at 7%, he finds another opportunity to invest at 10%. 
How much should he invest at the latter rate, if he wishes to make a total income of 8% on his investment.
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<pre>
Let x be the amount to invest at 10%.

Then the total interest is  0.07*4500 + 0.1x.


The equation for unknown x is this

    0.07*4500 + 0.1x = 0.08*(4500+x),

according to the problem.  Then

    0.07*4500 + 0.1x = 0.08*4500 + 0.08x,

    0.1x - 0.08x = 0.08*4500 - 0.07*4500

        0.02x    =         45

            x    =         45/0.02 = 2250.


<U>ANSWER</U>.  A merchant should invest additional $2250 at the rate 10% to get his goal.
</pre>

Solved.