mixture prob when one ingredient is pure

A

Angela McGrath

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I'm having alot of problems with my math teacher and the book itself. I'm the type of learner that needs multiple examples of how to perform an operation and all steps. This book gives you 1 example and its still confusing. I used to be really good at math but not anymore HELP! My math prob is this Mario Toussaint earned 12000 last year by giving tennis lessons. He invested part of the money at 3% simple interest and the rest at 4%. In one year he earned a total of 440 in interest. How much did he invest at each rate? :confused: thanks Angela
 
Angela McGrath said:
I'm having alot of problems with my math teacher and the book itself. I'm the type of learner that needs multiple examples of how to perform an operation and all steps. This book gives you 1 example and its still confusing. I used to be really good at math but not anymore HELP! My math prob is this Mario Toussaint earned 12000 last year by giving tennis lessons. He invested part of the money at 3% simple interest and the rest at 4%. In one year he earned a total of 440 in interest. How much did he invest at each rate? :confused: thanks Angela
Click to expand...

So we don't know how much he invested at 3%. Let's call that amount x. That means there is 12000 - x left that he invested at 4%. Does that make sense?

Given this, you then know:

x(0.03) + (12000-x)(0.04) = 440

Proceed....
 
srmichael said:
So we don't know how much he invested at 3%. Let's call that amount x. That means there is 12000 - x left that he invested at 4%. Does that make sense?

Given this, you then know:

x(0.03) + (12000-x)(0.04) = 440

Proceed....
Click to expand...

ok 0.03x + 48 + 0.04x = 440

0.03x +48 -48 +0.04x =440 - 48 = 392

0.03x + 0.04x = 392

0.07 (100 ) = 392 (100 )

7x = 39200
__ _____
7 7 = 5600

idk what im doing wrong ugh:(
 
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