Ok... So weighted Averages: An express train travels 90 Kilometers per hour from Smallville to Megatown. A local train takes 2.5 hours longer to travel the same distance at 50 kilometers per hour. How far apart are Smallville and Megatown? :huh: I can't figure this out... i got different answers every time I tried this. Question 2: Alice Gleason invested a prtion of $32,000 at 9% interest and the balance at 11% interest. How much did she invest at each rate if her total income from both investments was $3,200? :S I didn't even take the time to do this. It was extra credit.

For Question 2, I'd use a variable to define the initial portion invested, say 'y', and let the balance equal '32,000-y'. I'd use this to set up an equation with the sum of the two incomes from each amount invested at different rates equal to the total income, $3,200. Does that make sense? If not I could try to explain better. Let me know :) Oh, and what level of math are you in?

--oops, double post--

Post edited by: a_girl_made_pure, at: 2007/11/10 03:20

[b]a_girl_made_pure wrote:[/b] [quote]For Question 2, I'd use a variable to define the initial portion invested, say 'y', and let the balance equal '32,000-y'. I'd use this to set up an equation with the sum of the two incomes from each amount invested at different rates equal to the total income, $3,200. Does that make sense? If not I could try to explain better. Let me know :) Oh, and what level of math are you in?[/quote] 8th grade algebra 32,000-y =3,200 32,000-y-3,200=3,200-3,200 28800-y+y =+y 28800 = y What about the percents??

Sorry, I guess I didn't explain that very well. You'd add the income from the investments . . . 9% of y 11& of '32,000 - y' 0.09y + 0.11(32,000 - y)= 3,200

oh....

0.09y + 0.11(32,000 - y) = 3,200 0.09y + 3520 - 0.11y-3520 =3200-3520 0.09y -0.11y =-320/-0.11 0.09y +y /0.09 =-2909.1/0.09 2y /2 = -32323/2 Y = -1616.5 Is that right??:huh:

Post edited by: Smalltowngirl13, at: 2007/11/10 08:00

close;) You distributed correctly, and subtracting 3250 from both sides was right, but you don't need to divide by -0.11 0.09y and -0.11y are 'like terms,' since they have the same variable, so we can add them. Then we divide to get 'y' itself. Thus . . . 0.09y-0.011y=-320 -0.02y/-0.02=-320/-0.02 y=16,000 So the initial amount invested was $16,000. Then plug y=16000 into the '32000-y' to get the balance.

Post edited by: a_girl_made_pure, at: 2007/11/10 14:21

thank you for the help:) now I get it.

De nada. :)