How should I solve this Diophantine equation word problem?

  • Thread starter Thread starter Math100
  • Start date Start date
  • Tags Tags
    Word problem
Click For Summary

Homework Help Overview

The discussion revolves around solving a Diophantine equation related to a word problem involving the distribution of men, women, and children. The original poster attempts to find non-negative integer solutions for the equations 3x + 2y + 0.5z = 100 and x + y + z = 100, leading to a derived equation of 5x + 3y = 100.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the application of modulo arithmetic as a potential approach to solving the equation. The original poster expresses uncertainty about how to proceed after deriving the general solution. There is also a mention of the relevance of the problem's context to Diophantine equations.

Discussion Status

Participants are exploring various methods to approach the problem, including the use of modulo arithmetic. The original poster has articulated their current challenge, and others are contributing thoughts on the appropriateness of different mathematical techniques without reaching a consensus.

Contextual Notes

There is a note about the problem's origin in a specific section of Diophantine equations, which may influence the methods considered appropriate for solving it. The original poster's reference to needing to find particular solutions indicates a focus on the foundational aspects of the problem.

Math100
Messages
823
Reaction score
234
Homework Statement
Alcuin of York, 775. One hundred bushels of grain are distributed among 100 persons in such a way that each man receives 3 bushels, each woman 2 bushels, and each child 1/2 bushel. How many men, women, and children are there?
Relevant Equations
None.
Proof: Let x be the number of men, y be the number of women
and z be the number of children.
We need to find the solutions in the non-negative integers
for the Diophantine equation 3x+2y+0.5z=100 such that
x+y+z=100.

From x+y+z=100, we have that z=100-x-y.
Substituting z=100-x-y into the Diophantine equation
3x+2y+0.5z=100 and multiplying it by 2 produces:
5x+3y=100.

Applying the Euclidean Algorithm produces:
5=1(3)+2
3=1(2)+1
2=2(1)+0.

Now we have that gcd(5, 3)=1.
Note that 1##\mid##100.
Since 1##\mid##100, it follows that the Diophantine equation
5x+3y=100 can be solved.

Then we have 1=3-1(2)
=3-1(5-1(3))
=2(3)-1(5)

And now I'm stuck on this problem. I know I need to find the x0 and y0 in order to seek the general solution of the Diophantine equation. How should I go from here?
 
Last edited by a moderator:
Physics news on Phys.org
From ##3x +2y = 100## you could do some modulo arithmetic.

PS It shold be ##5x +3y = 100##, of course!

There are lots of solutions.
 
Last edited:
The modern version of this problem has bitcoins instead of bushels.
 
  • Haha
Likes   Reactions: berkeman
But this problem is from the section of Diophantine equations. Would it still be okay to do some modulo arithmetic without doing the back substitution for the Diophantine equation 5x+3y=100?
 
Math100 said:
But this problem is from the section of Diophantine equations. Would it still be okay to do some modulo arithmetic without doing the back substitution for the Diophantine equation 5x+3y=100?
Modulo arithmetic is as Diophantine as it gets!
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
2K
Replies
4
Views
2K
  • · Replies 19 ·
Replies
19
Views
3K
Replies
2
Views
1K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
Replies
1
Views
1K
Replies
1
Views
1K
Replies
2
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K