Ask Dr. Math

Elementary Archive

Browse Elementary Fractions & Decimals
Stars indicate particularly interesting answers or good places to begin browsing.

Selected answers to common questions:
    Adding and subtracting fractions.
    Finding a least common denominator (LCD).
    Dividing fractions.
    Comparing/ordering fractions; equivalent fractions.
    Reducing/simplifying fractions.
    Improper fractions and mixed numbers.
    Dividing decimals.
    Converting fractions to/from decimals.
    Rounding fractions and decimals.
    Fractions and repeating decimals.

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Why Decimal Division Works [04/24/2001]

Can you explain why (not how) the procedure of division with decimals works?

Why Does Division Convert a Fraction to a Decimal? [01/04/2009]

Why do you divide the denominator into the numerator to turn a fraction into a decimal? What is the math behind that process?

Why Does OF Mean Multiply? [12/04/2001]

I wanted to know why the word "of" means multiplication.

Why Do We Rationalize Fractions? [11/29/2005]

Why do we have to simplify fractions that have a radical in the denominator to remove that radical and rationalize the denominator? Why is that important?

Why Find the LCM? [10/07/1998]

Where do you use LCMs? How do they apply to real life?

Why Learn Fractions? [8/13/1996]

What is the point of learning fractions?

Why Round Decimals? [11/24/1997]

I have to explain to a 5th grader why we would want to round decimals.

Why the Decimal Point Goes Where It Does [09/21/2003]

My daughter is having trouble understanding why the first place before the decimal point is 'ones', and the first one after is 'tenths'.

Why the Decimal Point Moves when Multiplying by 10 [02/11/2005]

I am trying to explain why when you multiply a number by 10 you move the decimal point over one place to the right, and one place to the left when you divide by 10.

Why the Fraction Division Technique Works [11/27/2004]

Why do we need to flip the second fraction when we divide fractions?

Why We Need Decimals [10/23/1995]

Why do we need decimals?

Why Were Fractions Invented? [11/26/2007]

An overview of the history of fractions and the purpose they serve.

Working with Mixed Number Fractions [1/23/1996]

How do I subtract, add, or multiply a mixed number fraction?

Writing a Percent as a Fraction and Reducing the Result [05/03/2004]

I just can't seem to figure out how to convert a percent into a fraction, such as 20% = 20/100 = 1/5. All I know is that you put it into a fraction like 20/100 but after that I get stuck and I just don't know how to get the answer.

Writing a Remainder as a Reduced Fraction [08/29/2001]

I have to solve two division problems and write the remainder as a reduced fraction.

Writing Decimals from Words [10/05/1998]

Given a decimal written in words, how do you turn it into a decimal? In other words, how do you turn the words into numbers?

Writing Numbers with Hyphens [06/04/2003]

Why do we hyphenate one hundred-millionth, but we don't hyphenate one hundred million?

Written Form of Decimals [03/21/2001]

What is the correct way to write decimals?

Zero Before the Decimal Point? [10/06/2000]

What is the merit of writing the zero before the decimal point in numbers less than one, for example 0.25?

Zero in the Denominator [8/14/1996]

What is the value of 4/0 * 0/4?

Zeros after the Decimal Point [09/17/2001]

I have a group of students who just can't comprehend my explanation of how 3.70 is equivalent to 3.7 or 3.700 or 3.7000.

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