Please help me solve this and show me how you got the answer? Thank you.

Question

You Inherit $70,000 from a very wealthy grandparent, with the stipulation that for the first year, the money must be invested in two stocks paying 4% and 10% annual interest, respectively. How Much should be invested at each rate if the total interest earned for the year is to be 4000?

Answer 1

x = amount invested at 4%

y = amount invested at 10%

 

x + y = 70000  (this is the money invested

0.04x + 0.1y = 4000  (this is the interest)

 

Multiply the second by 10

 

0.4x + y = 40000  subtract this from the first

 

0.6x = 30000   divide by 0.6

x = 50000

 

You should invest $50,000 at 4% and $20,000 at 10%.