Math... story problems

[AmdEmAll]

I just can't figure out how to begin these story problems, im sure you folks can do these no problem.

- Adam's father had $6500 invested, some at 4.5% and some at 5%. He said if the amounts at each rate had been interchanged, the interest would have been $3.20 more. How much did he have invested at each rate?

This one I have no clue how to start.

- At 2 pm two cars start toward each other from towns 240 miles apart. If the rate of one car is 10 mph faster than the other, how fast does each car go if they meet at 5 pm?

Ok on this one, if they leave at the same time and one car is going faster how can they both get there at 5 pm?? shouldn't the faster car get there earlier?

BTW this is a Math 53 college class...

 

[Furyline]

Originally posted by: AmdEmAll
- At 2 pm two cars start toward each other from towns 240 miles apart. If the rate of one car is 10 mph faster than the other, how fast does each car go if they meet at 5 pm?

Ok on this one, if they leave at the same time and one car is going faster how can they both get there at 5 pm?? shouldn't the faster car get there earlier?

The cars meet at 5 pm, so they cover 240 miles total in 3 hours, so their closing speed is 80 mph. So one is going 45, the other 35.

 

[HN]

for the cars...there's no specific "there." Fast A--------------->5:00pm<-------Slow B

 

[AmdEmAll]

Thanks

Alright I think I understand the second problem now. what about the first?

 

[Mo0o]

Problem 1:

X+Y=6500

(.045X+.05Y)-(.05X+.045Y)= +-3.20

Just plug and chug

THere are two investments, $X and $Y. You know they have to add up to 6500 since thats all the dad has. THe total made from investments with normal interest rates would be .045X+.05Y (these are assigned arbitrarily). Then to find the difference you substract from the reverse (.05X+.045Y).

 

[KarenMarie]

you have to promise to post pics... or no one will help you.

sorry.

 

[AmdEmAll]

Originally posted by: KarenMarie
you have to promise to post pics... or no one will help you.

sorry.

pics of what?

 

[KarenMarie]

Originally posted by: AmdEmAll

Originally posted by: KarenMarie
you have to promise to post pics... or no one will help you.

sorry.

pics of what?

sorry.. hahaha!! it was a joke. VeggieFrog has a huge math question yesterday and in order to get her some help, i had to promise to post a pic of her afterwards... she did get help and i posted the pic.

it was a joke... sorry.

 

[AmdEmAll]

Originally posted by: KarenMarie

Originally posted by: AmdEmAll

Originally posted by: KarenMarie
you have to promise to post pics... or no one will help you.

sorry.

pics of what?

sorry.. hahaha!! it was a joke. VeggieFrog has a huge math question yesterday and in order to get her some help, i had to promise to post a pic of her afterwards... she did get help and i posted the pic.

it was a joke... sorry.

Heh yeah I remember reading that. I'm a guy though so no one wants to see pics of that.

 

[AmdEmAll]

Originally posted by: Mo0o
Problem 1:

X+Y=6500

(.045X+.05Y)-(.05X+.045Y)= +-3.20

Just plug and chug

THere are two investments, $X and $Y. You know they have to add up to 6500 since thats all the dad has. THe total made from investments with normal interest rates would be .045X+.05Y (these are assigned arbitrarily). Then to find the difference you substract from the reverse (.05X+.045Y).

I did (.045X+.05Y)-(.05X+.045Y) and I get 0

 

[audi]

*obligatory how the hell did you get into college post*

 

[OulOat]

Originally posted by: AmdEmAll

Originally posted by: Mo0o
Problem 1:

X+Y=6500

(.045X+.05Y)-(.05X+.045Y)= +-3.20

Just plug and chug

THere are two investments, $X and $Y. You know they have to add up to 6500 since thats all the dad has. THe total made from investments with normal interest rates would be .045X+.05Y (these are assigned arbitrarily). Then to find the difference you substract from the reverse (.05X+.045Y).

I did (.045X+.05Y)-(.05X+.045Y) and I get 0

How the hell did you get zero? List what you did

 

[AmdEmAll]

do I solve that problem using FOIL? I put it in the calc and subtracted them.

 

[akubi]

Originally posted by: audi
*obligatory how the hell did you get into college post*

i concur. i was going to answer them but i didn't believe they were really for college. thought it was a junior high student trying to get us to do his homework.

 

[akubi]

Originally posted by: AmdEmAll
do I solve that problem using FOIL? I put it in the calc and subtracted them.

ROFL!!!!

FOIL?? yes, you just proved you are in junior high school

 

[AmdEmAll]

Originally posted by: akubi

Originally posted by: AmdEmAll
do I solve that problem using FOIL? I put it in the calc and subtracted them.

ROFL!!!!

FOIL?? yes, you just proved you are in junior high school

Dont be a dick, this is MATH 53 and yes in a college.

 

[HN]

hey, i still do the alligator mouth thing when doing greater than/less than and it's never failed.

 

[akubi]

sorry it's just that I haven't heard of that mnemonic since jr high. you only use that for multiplying two binomials. notice the minus sign between the parentheses... all you have to do is distribute and subtract. no foil.

 

[AmdEmAll]

Originally posted by: HN
hey, i still do the alligator mouth thing when doing greater than/less than and it's never failed.

lol nothin wrong with that

btw I didn't even have algebra in high school so im taking it in college. I'm only required to get through math 113...

 

[OulOat]

Answer is simple. X=3570 and Y=2930.

 

[So]

most basic way to do it is by substitution.

2 eqn's 2 unknowns.

eq1 : x + y = 6500
eq2 : (5x + 4.5y) - (4.5x + 5y) = 3.2 (+/- signs dont really matter since all ti ould do is interchange your x & y) --> .5x - .5y = 3.2

now, I hate substitution, so I threw this into a matrix and got an answer:

[[1,1][.5,-.5]][[x][y]] = [[6500][3.2]]

Invert, multiply, and finish.

 

[So]

Originally posted by: OulOat
Answer is simple. X=3570 and Y=2930.

Your method checks to give a difference of $320

my answer...3253.20 and 3246.8 gives a difference of 3.2

(I have a .xls file to prove it, if you'd like)

 

[OulOat]

Originally posted by: So

Originally posted by: OulOat
Answer is simple. X=3570 and Y=2930.

Your method checks to give a difference of $320

my answer...3253.20 and 3246.8 gives a difference of 3.2

(I have a .xls file to prove it, if you'd like)

Remember you are working with percents

 

[So]

Originally posted by: OulOat

Originally posted by: So

Originally posted by: OulOat
Answer is simple. X=3570 and Y=2930.

Your method checks to give a difference of $320

my answer...3253.20 and 3246.8 gives a difference of 3.2

(I have a .xls file to prove it, if you'd like)

Remember you are working with percents

Ooh. Point. Let me check again.

 

[So]

Originally posted by: So

Originally posted by: OulOat

Originally posted by: So

Originally posted by: OulOat
Answer is simple. X=3570 and Y=2930.

Your method checks to give a difference of $320

my answer...3253.20 and 3246.8 gives a difference of 3.2

(I have a .xls file to prove it, if you'd like)

Remember you are working with percents

Ooh. Point. Let me check again.

Yup. You're right, I e-powned myself on JHS math. What's me EE degree going to me worth now?