How much was invested at each rate?

Question

Mrs. Alford invested $5100 in securities. Part of the money was invested at 2% and part at 5%. The total annual income was $138.

Answer 1

Let A = the 2% security and B = the 5% security

 

A + B = $5,100

.02A + .05B = $158

 

Express A in terms of B:

 

A = 5,100 - B

 

Substitute in second equaiton

 

.02(5,100 - B) + .05B = 158

102 - .02B + .05B = 158

.03B = 158 - 102

.03B = 56

B = 56 / .03 = 1,867

 

A + 1,867 = 5,100

A = $3,233