Parents: Help your child or teen

Online Volumes (Book Orders)
1,  Elements of Reason. 1996
1A. Pattern Based Reason  1995
1B. Math Curriculum Notes 1996
2. Three Skills for Algebra  1995
3.
_Why_Slopes_&_More_Math_1995

More Site Areas 
1.  Solving Linear Equations  2005
2.-Fractions-Rates-Proportns-Units-2006
3.  Algebra, Odds & Ends, HS level-2001
4.-Euclidean-Geometry/Complex No.s 
5.  Analytic Geometry/Functions 2006
6.  Number Theory. 2006-7
7.  Complex Numbers More 2001
8.  Calculus Introduction 2005
More Site Areas 
9   Real  Analysis 1995
10. Secondary IV? maths 2006-7
11. Math Education Essays  2006-7
12. LaTeX2HotEqn: 2004
13. Electric Circuits Etc  2007
14. Quebec Math Education 2004
15-Prequel-to-the-How-TOs-06-2008
How TOs/ Ref.-08- 2008
1. Arithmetic Reference
2. Algebra 
3. More Algebra 
4. Geometry  
5. More Geometry
6. Calculus
7. Logics in Maths


Employ an online or offline tutor at your own risk from 

AU:  tutorfinder.com.au
CDN :  findatutor.ca 
CDN: .i-tutor.ca
CDN: Montreal Tutors
NZ:   findatutor.co.nz
UK:   tutorhunt.com 
UK:  tutors4me.co.uk
USA:  wiziq.com
USA: ziizoo.com

YOU are better than YOU think. Show yourself  how:

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 For better work & study skills, read logic chapters 1 to 5  in  Three Skills for Algebra. Sooner is better. Good luck.

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 Logic Mastery
 Amazing, Amusing, Amorous,  Delicious, Delightful, Edifying, Strengthening Elixir. 
It eases work & learning difficulties Makes the hard easier. Opens eyes. Leads to greater precision.
in reading and writing

Do not leave here without it -  Logic mastery  will develops critical thinking, improve reading and writing, and give a firmer base for work and studies at many levels. Good luck.

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Caution: Site advice is approximately correct, for some circumstances, not all. Site How-TOs are logically developed, but not tried and tested. That leaves room for thought and refinement..

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After logic  (a) continue reading Three Skills for Algebra, chapters 8 to 14  and do so alongside site area on solving linear2007 Equations ; or (b) see this calculus starter lesson and Volume 3, Why Slopes  & More Math, chapters 2 to 6;


For online automated help in senior high school maths & calculus, visit  quickmath.com  For Automatic Calculus and Algebra Help with derivatives, integrals, graphs, linear equations, matrix algebra, visit calc101.com  With  overlap, each site quickmath & calc101offers a different range of services, some free, some not, all based on webmathematica. Good luck.


Explore collaborative whiteboards from groupboardtwiddla  or scriblink.


 Ratio of Decimal Fractions

A ratio of decimal fractions is a compound fraction 

M
N

in which the numerator and denominator are both decimals - proper or improper fractions expressible as whole number over a power of 10.

Imagine for some reason, the question how many times 0.23 meters went into the distance 4781.55 meters was met. The division algorithm above applies only to whole number divisors. So to obtain whole numbers, we ask how many times does 23 centimeters = 23 x (0.01 meters) go into 4781.55 meters = 478155 centimeters. The long division  of 478155 by 23 gives 20789 times completely with a remainder of 8 centimeters  = 0.08 meters leftover.

Shifting the Decimal Point

In general if M and N are given by decimal fractions then 

M   =  P 
10a
and   N   = 
10b

for some whole or natural numbers P, Q, a and b. Here we assume a and b give the number of digits after the decimal point in the finite decimal notation for M and N respectively, and we may also assume the ones digit in both P and Q are nonzero.  Now

M
N
 =  P 
10a
---

10b
 =   P 
10a
 *  10b
Q
 P*10b 
10a
 *  1
Q
P* 10b
  10a
-----
  Q 

The foregoing justifies the long division method of shifting the decimal point in the dividend  and divisor by number of decimal places in the divisor to obtain an integral (whole number) divisor Q

Another Twist: 

M
N
 =  P 
10a
---

10b
 =   P 
10a
 *  10b
Q
 P*10b 
Q*10a

The twist yields

456.89   456.89 x 1000      456890
------ = --------------  = --------
34.567   34.567 x 100       34567 

Long Division  - Remainder Analysis and Convergence

The equalities

M
N
 =  P 
10a
---

10b
 =   P 
10a
 *  10b
Q
 P*10b 
10a
 *  1
Q
P* 10b
  10a
-----
  Q 

 imply for the long division computation of M/N that   we can shift the decimal point in both the denominator or divisor N and dividend or numerator M to obtain an equivalent fraction in which the denominator is a whole number Q. 

Now for any whole number k,  long division

10k P = s(k) Q+ r 

where  0 < r < Q is a natural number. Therefore division by 10k Q gives

P
Q
 =    s(k) 
10k
 
10k
* r
Q

Here 

0 <  
10k
 *  r 
Q
 
10k

Therefore 

  s(k) 
10k

provides at least the first k digits of the decimal expansion of 

P
Q

beyond the decimal point.  The result 

P
Q
 =    s(k) 
10k
 +   
10k
* r
Q

can also (I presume) be obtained by continuing the long division process as well. 

Remark: The foregoing implies the decimal expansion of P/Q will either terminate or provide an increasing Cauchy sequence of decimal fractions s(k)/10k which converge to a limit. 

Exercise: Show computing P/Q to k decimal after the decimal point gives
M
N
 =  10b
10a
 *  P
Q

to  k+b-a places after the decimal point.

www.whyslopes.com
Number Theory

Back ] Up ] Next ]

Start of Number Theory

Origins of Counting or Tallying
Adding Wholes
Multipling Wholes
Distributive Law  Preamble
Distributive Law for Wholes
Consequences
More Consequences
What is a Fraction
Compound Fractions

Number Theory
Continued


Decimal Place Value
Place Value Reinforcement
Comparison Method
Addition Method
Subtraction Methods
Multiplication Methods
Division Methods
Remainder Arithmetic I
Primes & Composites
Primes Factorization Theorem
Primes & Composites
Prime Factorization Aids
Prime Factorization Examples
Counting  Whole No.  Factors
Arithmetic Videos
Square Roots  & Primes
Long Division Continued
Fractions & Decimals
Fractions as Decimals
1 = 0.999 Recurring
Infinite Decimals Expansion Arithmetic
Ratio of Simple Fractions
Ratio of Decimal Fractions
Unsigned Reals Numbers
Signed Coordinates
Plane Vectors
Horizontal Vectors
Adding Vector Multiplies
Adding Signed Numbers
Multiplying Signed Numbers
Distributive Law for Reals
Real Numbers Axioms
Remainder Arithmetic II

Related Site Pages:

For online automated help in senior high school maths & calculus, visit  quickmath.com  For Automatic Calculus and Algebra Help with derivatives, integrals, graphs, linear equations, matrix algebra, visit calc101.com  With  overlap, each site quickmath & calc101offers a different range of services, some free, some not, all based on webmathematica. Good luck

Food for thought: Try the Twiddla Whiteboard. In principle, it  allows to people to draw and chat together online on a copy of this webpage or a clean sheet. The chat may be via text or audio.  Visit www.twiddla.com to set up whiteboards to work with the webpage of your choice..

 

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Wordy Site Tour:  Not too Bad Vol 2. Foreword 1A Foreword2  Logic Puzzles,  
What is a Variable
  Calculus Starter Guide  Vol 1 Foreword,  
 
 
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