My Math Forum  

Go Back   My Math Forum > High School Math Forum > Algebra

Algebra Pre-Algebra and Basic Algebra Math Forum


Thanks Tree2Thanks
Reply
 
LinkBack Thread Tools Display Modes
February 22nd, 2018, 08:31 AM   #1
Newbie
 
Joined: Feb 2018
From: dont share

Posts: 4
Thanks: 0

Algebra Problem Solving Question

I need help on this algebra word problem as I don't know how to work out the number of stamps and I don't know how to approach this question.
Thank You and help is appreciated.

Question:
jjjjjjj.jpg

Last edited by skipjack; February 22nd, 2018 at 02:24 PM.
nstar348 is offline  
 
February 22nd, 2018, 08:49 AM   #2
Senior Member
 
Joined: May 2016
From: USA

Posts: 1,038
Thanks: 423

The first step is to assign letters to represent the numbers that may be relevant but that you do not yet know. What letters have you assigned to what?
JeffM1 is offline  
February 22nd, 2018, 09:03 AM   #3
Newbie
 
Joined: Feb 2018
From: dont share

Posts: 4
Thanks: 0

a = alex b = bryan c = calvin

I have found that

$\displaystyle a = \frac{b+c+78}{2}$

and that

$\displaystyle b = \frac{(b+c+78/2)+ c +78}{3}$

and that

c can be found by adding a and b and 78, but I don't know how I could do that as the equations look complicated and after many attempts I still can't try to solve it.

Last edited by skipjack; February 22nd, 2018 at 02:27 PM.
nstar348 is offline  
February 22nd, 2018, 09:29 AM   #4
Senior Member
 
Joined: May 2016
From: USA

Posts: 1,038
Thanks: 423

Quote:
Originally Posted by nstar348 View Post
a = alex b = bryan c = calvin
Great. Always the way to start. You have three unknowns. Therefore you need three numeric clues involving the unknown numbers.

Using your letters, write down what you know about numbers that pertain to your unknowns.

The second sentence gives you a clue. How do you write it down in algebraic notation? The third sentence gives you another clue. How do you write it down in algebraic notation? The fourth sentence gives you one more clue. How do you write it down in algebraic notation?

You now have a pure algebra problem.

Do you know what to do next?

Last edited by skipjack; February 22nd, 2018 at 03:08 PM.
JeffM1 is offline  
February 22nd, 2018, 09:33 AM   #5
Global Moderator
 
greg1313's Avatar
 
Joined: Oct 2008
From: London, Ontario, Canada - The Forest City

Posts: 7,814
Thanks: 1046

Math Focus: Elementary mathematics and beyond
One of nstar348's previous posts was auto-moderated and therefore hidden. I've approved it so it is now visible.
greg1313 is offline  
February 22nd, 2018, 09:38 AM   #6
Newbie
 
Joined: Feb 2018
From: dont share

Posts: 4
Thanks: 0

The reply I made before you replied with my workings out - that is what I think I have to do next, but I don't know after.

Last edited by skipjack; February 22nd, 2018 at 02:29 PM.
nstar348 is offline  
February 22nd, 2018, 09:53 AM   #7
Global Moderator
 
greg1313's Avatar
 
Joined: Oct 2008
From: London, Ontario, Canada - The Forest City

Posts: 7,814
Thanks: 1046

Math Focus: Elementary mathematics and beyond
$\displaystyle D = 78$

$\displaystyle A = \frac{B + C + D}{2}\Rightarrow2A=B+C+78\Rightarrow2A-B-C=78$

$\displaystyle B = \frac{A + C + D}{3}\Rightarrow3B=A+C+78\Rightarrow-A+3B-C=78$

$\displaystyle C = \frac{A + B + D}{4}\Rightarrow4C=A+B+78\Rightarrow-A-B+4C=78$

The RHS is a system of 3 equations in 3 variables but there is a shortcut:

$$-A-B+4C=78\implies A+B=4C-78$$

So all you have to do is find $C$ and substitute that value into the equation above. Can you proceed?
greg1313 is offline  
February 22nd, 2018, 10:05 AM   #8
Newbie
 
Joined: Feb 2018
From: dont share

Posts: 4
Thanks: 0

I'm a bit confused at how I could work out c when I don't have a number value for a and b.

Last edited by skipjack; February 22nd, 2018 at 02:31 PM.
nstar348 is offline  
February 22nd, 2018, 10:16 AM   #9
Global Moderator
 
greg1313's Avatar
 
Joined: Oct 2008
From: London, Ontario, Canada - The Forest City

Posts: 7,814
Thanks: 1046

Math Focus: Elementary mathematics and beyond
The problem asks you to find the number of stamps that Alex and Bryan have altogether.

We have arrived at the equation A + B= 4C - 78 so, by finding a value for C (which is 72) we write A + B = 4 * 72 - 78 = 210, so Alex and Bryan have a total of 210 stamps. Can you find C using the given information?
Thanks from nstar348
greg1313 is offline  
February 22nd, 2018, 03:09 PM   #10
Global Moderator
 
Joined: Dec 2006

Posts: 19,063
Thanks: 1621

As 8a + 9b + 20c = 4(b + c + 78) + 3(a + c + 78) + 5(a + b + 78) = 8a + 9b + 7c + 12(78),
13c = 12(78), and so c = 72.
Thanks from greg1313
skipjack is offline  
Reply

  My Math Forum > High School Math Forum > Algebra

Tags
algebra, problem, question, solving



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Algebra - Year 10 Problem Solving pianist Algebra 2 January 10th, 2017 01:44 AM
Algebra problem solving 3 kingkos Algebra 2 January 7th, 2014 03:35 PM
Algebra problem solving 2 kingkos Algebra 2 January 6th, 2014 04:08 PM
Algebra problem solving kingkos Algebra 2 January 6th, 2014 04:05 PM
Algebra problem - Solving for b Klyka Algebra 6 December 21st, 2008 03:14 PM





Copyright © 2018 My Math Forum. All rights reserved.