Question

Mr. Wilson invested money in two accounts. His total investment was $9,000. If one account pays 4% in interest and the other pays 12% in interest, how much did he invest in each account if he earned a total of $680 in interest in 1 year?
@iambatman

Answer 1

Let the amount earning 4% be x.
Let the amount earning 12% be y.
x + y =9000 .............................(1)
0.04x + 0.12y = 680 ................(2)
Now just solve the simultaneous equations. Can you do that?

Answer 2

I think I can

Answer 3

@iambatman batman i need you ! lol

Answer 4

Look at @kropot72 explanation :P, it's the same thing as the last question just with more words.

Answer 5

Exactly! It confuses me lol I don't even know which one to start with

Answer 6

It doesn't matter, but you can pick equation one, since it's easier to isolate x or y.

Answer 7

x=-y+9000?

Answer 8

Yeah :D

Answer 9

By rearranging (1) you can find y in terms of x as follows:
y = 9000 - x
Now substitute the value of y into equation (2) giving:
0.04x + 0.12(9000 - x) = 680 ...............(3)
Can you multiply out equation (3) and combine like terms to solve for x?

Answer 10

Oh goodness, I'm gonna have a heart attack over here lol

Answer 11

You can do it either way cookii

Answer 12

y=4000

Answer 13

Correct!

Answer 14

Now just sub that in one of the equations to get x :p

Answer 15

x=5000!

Answer 16

Pro

Answer 17

whooooa, I've never done math so fast in my life! I have almost 10 minutes to finish this quiz!

Answer 18

It's because I'm batman.

Answer 19

lol is 12% 5000 & 4% is 4000?

Answer 20

x = 4%
y = 12%

If you used Kropots explanation.