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Noob88
Member
Joined: 23 Nov 2005
Posts: 239
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 Posted: 18 Dec 2007 09:31:22 pm Post subject: |
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Ok, my younger brother had interest problems to do for homework tonight and I was able to do it all because it was just simple review. Then I got to the last problem, and I was completely baffled on how to set it up as it was different from the rest of them. Here is the problem, if anyone could show me how to set it up and solve it, that would be amazing.
If Emma had earned one fourth of a percent more in simple annual interest on an investment, the total interest for one year would have been $45 greater. How much money did she invest at the beginning of the year? In your cheart, set up two investments: one for what Emma actually did invest and the other which represents what she would have received with the 1/4% higher interest rate.
The other problems were all simple interest problems and were easy to solve, but for some reason this one has me stumped. I'm not sure if he figured it out or not yet, but I've been looking at it and I just cannot get it at all and I know I'm going to feel dumb when somebody explains it to me  |
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luby
I want to go back to Philmont!!
Calc Guru
Joined: 23 Apr 2006
Posts: 1477
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| Posted: 18 Dec 2007 09:50:01 pm Post subject: |
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well, if .25%X =45 ,with X being the inital amount so, naturally, X is 18000.
Did that help? |
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Noob88
Member
Joined: 23 Nov 2005
Posts: 239
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| Posted: 18 Dec 2007 09:52:22 pm Post subject: |
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Not so much... Here is what another one was
Jim invested $9450, part at 8% simple annual interest and the rest at 11% simple annual interest. He earned TWICE AS MUCH interest at 11% as he did at 8%. How much money did he have invested at 11%?
.11x=2[.08(9450-x)]
.11x=2(756-.08x)
.11x=1512-.16x
1512=.27x
x=5600$
See, but on the last problem, I just have no idea what to do could you walk me through it? |
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luby
I want to go back to Philmont!!
Calc Guru
Joined: 23 Apr 2006
Posts: 1477
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| Posted: 18 Dec 2007 10:22:23 pm Post subject: |
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Sure. Let's start with an example. 10% of 100 is 10, correct? well, 10.25% of 100 is 10.25. .25% of 100 is .25, so therefore we can assume that x+.25% - x% will be the same as .25%, so no matter what Emma earned, if .25% more is $45 then .25%InitialValue is $45.
Then, you can multiply both sides by 4 to get 1% = $180 and 100% (or InitialValue) is $18000. |
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