Question

Linda invests $13,000 for one year. Part is invested at 4%, another part at 5%, and the rest at 7%. The total income from all 3 investments is $705. The combined income from the 4% and 5% investments is $75 more than the income from the 7% investment. Find the amount invested at each rate
(can somebody please help me solve this problem, i am completely lost)

Answer 1

cant be too bad

Answer 2

let amount invested at 4% be x

ammount at 5% be y

amount at 7% be z

Answer 3

we know that the total amount invested is 13000

so x+y+z = 13000 ( one eqn )

Answer 4

now, assuming simple interest ( which I think is what they want )

Answer 5

I = Prn

Answer 6

income from $x = x (0.04)(1) =0.04x

Answer 7

x*1.04+y*1.05=z*1.07

With only one year it has to be simple interest.

Answer 8

so

^ thats another eqn there

Answer 9

and last condition gives another eqn

0.04x +0.05y = 75 + 1.07z

Answer 10

lol that guys eqn was wrong

Answer 11

yeah it was, sorry, fiddling about now

Answer 12

should have been 0.04x + 0.05y + 0.07z = 705

Answer 13

so


x+y+z = 13000


0.04x + 0.05y + 0.07z = 705

0.04x +0.05y = 75 + 1.07z

Answer 14

there eqns, three unknowns

you can solve, im not doing boring pointless albegra

Answer 15

algebra

Answer 16

no EDIT :

x+y+z = 13000


0.04x + 0.05y + 0.07z = 705

0.04x +0.05y = 75 + 0.07z

made a little mistake when copying the second eqn

Answer 17

they should have it so you can delete posts z :|

also, if you were to want to solve these eqns, the best first step would be to subtract eqns 2 and 3

Answer 18

yeah just word problems arent my thing :(