How to do this using series. Rep as ratio of two integers

Click For Summary

Homework Help Overview

The discussion revolves around expressing the repeating decimal 10.1(35) as a ratio of two integers. Participants are exploring methods related to geometric series and algebraic manipulation to achieve this representation.

Discussion Character

  • Exploratory, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Some participants attempt to express the number using geometric series, while others explore algebraic methods involving subtraction of equations. There are questions regarding the setup of equations and the manipulation of decimal places.

Discussion Status

Participants are actively sharing different approaches and questioning each other's methods. Some guidance has been offered regarding the alignment of repeating parts in the equations, but there is no explicit consensus on the correct method yet.

Contextual Notes

There appears to be confusion regarding the correct manipulation of the decimal and the setup of equations, with some participants noting discrepancies in their calculations and assumptions about the repeating decimal.

Jbreezy
Messages
582
Reaction score
0

Homework Statement


Express the number as a ratio of integers.
10.1(35) = 10.135353535 the part in the left in () is where is is over lined to indicate it is repeating



Homework Equations




Geometric series

The Attempt at a Solution



10.1(35) = 10.1 + .035 = (101)/ (1000) + (35/10^3 + 35/10^6...)

= 101/1000 + ((35/1000)/(1-(1000)) = .1360350
Clearly wrong. What did I mess up
 
Physics news on Phys.org
jbreezy said:

Homework Statement


express the number as a ratio of integers.
10.1(35) = 10.135353535 the part in the left in () is where is is over lined to indicate it is repeating



Homework Equations




geometric series

The Attempt at a Solution



10.1(35) = 10.1 + .035 = (101)/ (1000) + (35/10^3 + 35/10^6...)

= 101/1000 + ((35/1000)/(1-(1000)) = .1360350
clearly wrong. What did i mess up

10.1 ≠ 101/1000.
 
There's another way to go at this, as well.
Let S = 10.1353535...

Then 1000S = 10135.353535...
and 10S = 101.353535...

Subtract the 2nd equation from the first and solve for S.
 
Yeah that is actually what I did but I did it different. I said that it was Because I thought that you had to move the decimal to the end of the first repeating number.So in my case I said 10.1(35) the I have to move it to after the 5 so I multiply by 1000. My two equations will read.

S = 10.135353535
1000x = 10135.353535
Do the subtraction and you get 999x = 10125 So I ended up with 375/37
Why did you have 10S I just had x
 
Jbreezy said:
Yeah that is actually what I did but I did it different. I said that it was Because I thought that you had to move the decimal to the end of the first repeating number.So in my case I said 10.1(35) the I have to move it to after the 5 so I multiply by 1000. My two equations will read.

S = 10.135353535
1000x = 10135.353535
Do the subtraction and you get 999x = 10125 So I ended up with 375/37
No you don't. 10135.353535... - 10.135353535... ≠ 10125
Jbreezy said:
Why did you have 10S I just had x
So that the repeating part lines up in both numbers.
 
1000S = 10135.353535...
10S = 101.353535..

Subtract

990S = 10034 ---> S = 5017/495
 
That's more like it...

And of course you can check by doing the division.
 

Similar threads

  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 28 ·
Replies
28
Views
5K
  • · Replies 12 ·
Replies
12
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K