Algebra word problem

Question

A man invested $5000 partly at 4% and partly at 6%, so that he earned $275 total interest. What amount did he invest at each rate?

Answer 1

Daniella,

 

This problem can be solved by writing it out as an equation. Interest = Principal*Rate*Time (I=p*r*t).

 

Break this down into the sum of two separate investments, where:

 

Interest = Principal 1 * Rate 1 * Time + Principal 2 * Rate 2 * Time.

 

This equation can be simplified to Interest = (Principal 1 * Rate 1 + Principal 2 * Rate 2) * Time

 

 

Interest = $275

Principal 1 = X

Rate 1 = 0.04

Principal 2 = Y

Rate 2 = 0.06

Time = 1 (I assume)

 

 

We have two unknowns, therefore we must have two equations to solve for these unknowns.

 

 

$275 = (0.04*X + 0.06*Y) * 1 

 

X + Y = $5,000

 

Using these two equations to solve for your unknowns will give you the solution to your problem.

 

I hope this was helpful,

 

Brendan