Question

a total of $21,000 is invested in two bonds that pay 4% and 7.5% simple interest. The bond with 7.5 % interest rate earned 6 times as much interest. as the bond with a 4 % interest. rate. how much is invested in each bond? what was the total interest earned?

Answer 1

21000=a+b
ax.075xt=6xbx.04xt
t cancels out
a=3.2b
21000= 3.2b+b
21000=4.2b
b=5000
a=16000

account with 7.5% had 16000 invested in it.
account with 4% had 5000 invested in it