SOLUTION: I can not figure out the formula for the folliwng problem. Robert inherited $4000 from grandmother. Part was invested at 5% while the rest was invested at 6.5%. The interest for t

Question 7241: I can not figure out the formula for the folliwng problem.
Robert inherited $4000 from grandmother. Part was invested at 5% while the rest was invested at 6.5%. The interest for the yearw as $227. How much was invested at 6.5%
Answer by ichudov(507) (Show Source): You can put this solution on YOUR website!
say he invested X at 5% and Y at 6.5%. X+Y is 4,000. Interest is 0.05X+0.065Y = 227.

Solved by pluggable solver: SOLVE linear system by SUBSTITUTION

Solve:
We'll use substitution. After moving 1*Y to the right, we get:
, or . Substitute that
into another equation:
and simplify: So, we know that Y=1800. Since , X=2200.

Answer: .

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