Some Algebra

S

SingularPoint

Thread Junky
Joined
Nov 20, 2009
Messages
926
I have a upcoming test on Algebra, math is usually a subject I don't have to much trouble with but this question confuses me. :facewall:
"Wally has a dish full of nickels, dimes and quarters worth a total of $6.50. He has three times as many nickels as dimes, and eight more dimes than quarters. How many of each coin does he have?"
So I did broke it down using one variable. "n" for number of nickels
5n + 1/3(10n) + 1/3(25n) - 8 = 650
So I multiplied by 3/1 to simplify. 15n +10n + 25n - 24 = 1950
50n = 1974
n = 39.48 which rounds to 40
n=40
dimes = 13.3
quarters = 5
But that ends with $4.58 total.
Help would be much appreciated, and I apologize if this is the wrong section.
 
ugh. sorry singular. haha i kinda just used trial and error.

no real formula.

i knew that the number of nickels had to be a multiple of 3 while the number of dimes had to be divisible by 3. and then you subtract 8 to get the number of quarters. So i figured the number of nickels had to be great so i just tried 50, came up a bit short, and then i tried 51 and it worked. hahaha
 
Using "n" as number of nickles, "q" as number of quarters, and "d" as number of dimes:

Given: n is 3xd, or n=3d
Given: q is d-8, or q=d-8

Setup:
Code: 
0.05n + 0.10d + 0.25q = 6.50

Just multiplying the number of a certain element by it's value to get the total value of each element. Do a quick check to make sure you're right. Two nickles makes ten cents, right? Does 0.05*2 = 0.10? Yes? Good. Same thing does on with each variable. We know the sum is 6.50. Given.

After this, we plug in the formulas derived from he given statements to get:
Code: 
0.50(3d) + 0.10(d) + 0.25(d-8) = 6.50
From there, distribute everything to get:
Code: 
0.15d + 0.10 d + 0.25d - 2 = 6.50
Combine like terms to get:
Code: 
0.50d - 2 = 6.50
Bring the two to the other side (add two to both sides) to get:
Code: 
0.50d = 8.50
Divide both sides by 0.50 (or multiply by 2, same thing) to get:
Code: 
d = 17

So now we know the number of dimes. All that's left is to plug into the formulas we derived from the givens.

Code: 
n=3d; n=3(17) ; n=51
q=d-8; q=17-8; q=9

There. Not so bad, right? Once you know how to set it up, you're golden in Algebra.

EDIT: Oddly enough, I'm cramming my Calculus work in right now. Reminds me of my AP Chem days - I would procrastinate from doing my homework by doing other people's homework on Yahoo Answers. xD
 
Last edited:
Thanks man! You really helped me out here, as my grades are borderline 80% and if I don't make a A this term I'm royally boned :P

Good luck with the Calculus stuff, I tried it a year or two back and it blew my mind.
 
I'm currently enrolled and taking Calculus III and concurrently take the second half of Mechanical Physics for Engineering majors. I'm great at math but cal is about as boring as numbers can get. BUT, physics is a practical use of calculus and that is great!.
 
Gypsy said:
Wow. I'm curious where you go to school? They wouldn't even let us sign up for calculus until we had Algebra, Algebra II, Geometry, Trigonometry, and other math classes.

http://www.math.unb.ca/ready/paper/

That's quite a bit beyond "how many nickels does Wally have?"
Click to expand...

Oddly enough, I can do just about everything on that site but I didn't immediately know how to answer the nickels problem :O.

For the record, Integral Calculus is the opposite of fun.
 
still in high school taking AP Calc AB and AP Physics. I like your sig there toasted, but I feel like bruce wayne would be the derivative of batman as opposed to the integral.
 
SingularPoint said:
Thanks man! You really helped me out here, as my grades are borderline 80% and if I don't make a A this term I'm royally boned :P

Good luck with the Calculus stuff, I tried it a year or two back and it blew my mind.
Click to expand...

haha i'm glad someone better than me was able to help you out more. best of luck with everything else!
 
Haha, I have one more question that bothers me, but I'll work on that on my own.

As for my earlier Calculus experience, I've been thinking around.
 
Endiment said:
still in high school taking AP Calc AB and AP Physics. I like your sig there toasted, but I feel like bruce wayne would be the derivative of batman as opposed to the integral.
Click to expand...

Yeah, yeah. I found it on some "25 Greatest Exam Answers" article. Guy can't even get his own question right :P
 
You must log in or register to reply here.

Latest posts

Back
Top