Answer:
Step-by-step explanation:
let amount invested at 12%=x
amount invested in 10 %=y
amount invested in 8 %=z
z=2x
x+y+z=290,000
x+y+2x=290,000
3x+y=290,000
multiply by 5
15x+5y=1,450,000 ... (1)
12/100 x+10/100 y+8/100 z=27,600
12x+10 y+8z=2,760,000
6x+5y+4z=1,380,000
6x+5y+4(2x)=1,380,000
14x+5y=1,380,000 ... (2)
(1)-(2) gives
x=1,450,000-1,380,000=70,000
z=2(70,000)=140,000
70,000+y+140,000=290,000
y+210,000=290,000
y=290,000-210,000=80,000
invested in 12 %=$ 70,000
invested in 10 %=$ 80,000
invested in 8 %=$ 140,000
(b)
annual income from 12 %=12/100 ×70,000= $8,400
annual income from 10 % =10/100×80,000=$ 9,600
annual income from 8 %=8/100×140,000= $11,200
