# 2 Interest Rates. Find Invested Amts: Shelley invested $7000, part at 7%, part at 11% #### jeff221xD ##### New member Please More Help. thx Shelley invested$7000, part at 7% and the rest at 11%. If her total return for one year was $690, how much was invested at each rate? My work: So I thought I should add the 2 percentages together to make 18% And then I don't know what to do. Help thanks. #### mmm4444bot ##### Super Moderator Staff member Shelley invested$7000, part at 7% and the rest at 11%. If her total return for one year was $690, how much was invested at each rate? My work: So I thought I should add the 2 percentages together to make 18% And then I don't know what to do. We cannot add the interest rates. Sad, I know, but bankers are not willing to do that. Does your math class have a textbook? If so, there ought to be some examples of this type of exercise. (Use the index, to look for a section that covers "Systems of Two Equations".) If you don't have a textbook, here are some links to examples. Study one or two, then please try your exercise again. http://www.umsl.edu/~defreeseca/intalg/ch8extra/interest.htm http://www.sosmath.com/soe/SE2001/SE2001.html https://www.youtube.com/watch?v=WRWc8mly4i8 PS: Please also read the forum guidelines. Thanks! :cool: #### JeffM ##### Elite Member Please More Help. thx Shelley invested$7000, part at 7% and the rest at 11%. If her total return for one year was $690, how much was invested at each rate? My work: So I thought I should add the 2 percentages together to make 18% And then I don't know what to do. Help thanks. Some bankers may dream of adding interest rates (on loans), but the law and competition discourage it. The first thing to do in virtually every word problem is to identify what RELEVANT numbers you don't know and assign a symbol to each along with a brief description. What don't you know that is relevant to this problem? The dollars invested at each rate. It may be hard to know what you perhaps should, but it usually is easy to identify what you don't know. $$\displaystyle \text {Amount invested at } 7\% = x.$$ $$\displaystyle \text {Amount invested at } 11\% = y.$$ To solve two unknowns you need two numerical facts as clues? What are they? Last edited: #### stapel ##### Super Moderator Staff member Shelley invested$7000, part at 7% and the rest at 11%. If her total return for one year was \$690, how much was invested at each rate?

My work:

So I thought I should add the 2 percentages together to make 18%
And then I don't know what to do.
Hmm... They were supposed to have covered this stuff in class, before assigning homework on it. It appears that they didn't....

To learn the basic terms and techniques, try here. Once you have learned the basic terms and techniques, please attempt the exercise. If you get stuck, you can then reply with a clear listing of your thoughts and efforts so far. Thank you!

P.S. It's okay to use what you know from real life. You know that rates of speed don't add; for instance, if you drove 35 mph down one street and then 45 mph down another, you know that you never when 80 mph at all, let alone down both streets! If you pay 29% interest on the balances on each of four credit cards, you know that doesn't mean that you pay 116% on everything. Use this knowledge when interpreting word problems!

#### tkhunny

##### Moderator
Staff member
part at 7% and the rest at 11%.
Just to be clear, when you combine these two, you will get something between 7% and 11%. If you manage ANTHING else, something has gone seriously wrong.