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This is my first topic so please be kind. The question below is an IR question that I am having trouble setting up. Any input from members would be greatly appreciated.

KapTeacherEli · Answer

Hi Crindo,

You're looking at a classic mixture problem--you can check out  here  for a little more detail on them.

Basically, we are "mixing" 4% and 8% interest, to get  r % interest. Although this problem is discussing interest rates, we shouldn't be distracted, because we don't need any fancy formulas for calculating them. We can use the mixture formula alone--which is, conveniently, given to us by the question stem!

r  is given to us as 5%, so we can plug that in to the mixture formula given in the question stem. Do so, then remove fractions:

5( x + y ) = 4 x  + 8 y

Distribute:

5 x  + 5 y  = 4  x  + 8 y

Combine like terms:

x  = 3 y

Now, many TPA problems will not have a single algebraic solution. This is two variables in one equation; it's unsolvable. But we have a limited number of choices to solve for. Plug them in, and we'll find that the only set of answers that works is  x  = 96,  y  = 32

crindo2 · Answer

Thanks so much Eli!

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