Solving for Recurring Numbers: Techniques and Applications

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Discussion Overview

The discussion revolves around techniques for expressing recurring decimals as fractions, specifically focusing on the recurring number 0.1454545454545... Participants explore various methods to derive the fractional representation without the use of calculators.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant seeks help in expressing the recurring decimal 0.1454545454545... as a fraction, indicating a need for clarification on the technique involved.
  • Another participant suggests a method involving multiplying the decimal by 100 to shift the recurring part, leading to the equation 99x = 14.4, which simplifies to x = 14.4/99.
  • A different approach is presented where the decimal is first multiplied by 10, resulting in 10x = 1.454545..., followed by another multiplication by 100, leading to 900x = 144, ultimately giving x = 144/900.
  • One participant corrects a minor error in their previous calculation, noting that the correct equation should be 1000x - 10x = 990x, resulting in x = 144/990.
  • Another method is introduced that involves working with the geometric series, where the recurring part is treated as a series, leading to a fractional representation of the sum.
  • Some participants express a preference for more elementary methods over the geometric series approach, indicating a variety of perspectives on the complexity of the solutions.

Areas of Agreement / Disagreement

Participants present multiple competing methods for solving the problem, with no consensus on a single preferred technique. Each method yields similar results but varies in approach and complexity.

Contextual Notes

Some methods rely on specific assumptions about the manipulation of recurring decimals, and the discussion includes corrections to earlier claims without resolving which method is superior.

Who May Find This Useful

Readers interested in mathematical techniques for converting recurring decimals to fractions, particularly students or individuals seeking to understand various problem-solving approaches in mathematics.

FateMaster
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Hihi... I am stumped at this question... I know there is a techique in doing this question... But i forget oredi... Help please...


Express this recurring number at a fraction of a/b...
Recurring number ---> 0.1454545454545...

Plz explain to me the technique used... No calculators allowed... :-p
 
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The general trick is to equalise it x multiply by 10^(the number of digits recuring) then take away the orriginal number.

Using your problem as an example.

x = 0.1454545454545...

2 digits are recurring so multiply it be 100

100x = 14.54545454545...

Take away the orriginal number:

100x - x = 14.54545454545... - 0.1454545454545...

Take this a digit at a time:

99x = 14.40000000000...

99x = 14.4

That should be a little easier to solve now :smile:
 
Stupid me... :smile:

Thankx... lol... So its this easy...

Hehe... Thankx for your help mate... :blushing: :biggrin:
 
Slightly different way:

Because there is that "1" before the recurring "45", first multiply by 10:

10x= 1.454545...

Now multiply that by 100: 1000 x= 145.454545... and subtract

1000x- 10x= 900x= 144 so x= 144/900

Of course, that gives exactly the same result.
 
HallsofIvy said:
1000x- 10x= 900x= 144 so x= 144/900

Of course, that gives exactly the same result.

Oh, no. Minor snag here. 1000x - 10x = 990x. So the answer really is 144/990. :smile:

You may simplify 144/990, of course.
 
I like the fact that there are many different ways for solving problems. Here's another method. Not that it is really different: it just differs slightly from all the others.

x = 0.1454545...
10x = 1.454545...

10x - 1 = 0.454545...

We can work out 0.454545... to be 45/99 (100z - z = 45).

10x - 1 = 45/99
10x = (99 + 45)/99
10x = 144/99
x = 144/990
 
also can do it by "geometric series", really the same again, but done once for all:

i.e. .1 + .045454545...

is .1 Plus the geometric series with initial term a= .045 and ratio r= 1/100, so the sum

is a + ar + ar^2 +...= a/(1-r) i.e. .045/(99/100) = (4.5)/99, so the answer is

.1 + this, as before.

I really do not like this answera s the others's answers are more elementary. but at least it shows how to algebraize their methods.
 

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