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Flashcards in Fractions Deck (13)
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1

Rule for adding and subtracting fractions

Denominator must ALWAYS be the same. So find the LCD

2

Quick check for why
a/(b + c)
doesn’t equal
a/b + a/c

Replace everything with 1:
1/2 doesn’t equal 2/1

3

To add or subtract two fractions

we use a common denominator:
a/b + c/d = ad + bc / bd

- multiply top and bottom by the other denominator to get the quickest common denominator fractions.

- ALWAYS PUT + - in parentheses

4

Multiply fractions
a/b x c/d

ac / bd

5

Negative sign rule for fractions


a
-a/b = - — = a/-b
b

6

To divide two fractions...

invert and multiply:
a/b
—— = a/b x d/c = ad/bc =a/c x d/b
c/d

7

Simplifying Complex Fractions Method 1

Method 1
Key steps:
1) Create a single fraction in the numerator and denominator.
2) Apply the division rule of fractions by multiplying the numerator by the reciprocal or inverse of the denominator.
3) Simplify, if necessary.

https://www.chilimath.com/lessons/advanced-algebra/simplifying-complex-fractions/

8

Simplifying Complex Fractions Method 2

Method 2

Key steps:
1) Find the Least Common Denominator (LCD) of all the denominators in the complex fractions.
2) Multiply this LCD to the numerator and denominator of the complex fraction.
3) Simplify, if necessary.

Usually the fastest method


https://www.chilimath.com/lessons/advanced-algebra/simplifying-complex-fractions/

9

Improper fraction

Numerator > denominator

10

Turn a decimal into a fraction

Put it over the corresponding 10’s figure and simplify

11

Find common denominators for fractions

- multiply top and bottom by the other denominator to get the quickest common denominator fractions.

12

For fraction problems, always remember

1) ALWAYS PUT + - in parentheses, they’re always linked

2) multiplication follows the distributive, commutative and associative laws.

3) Use the two methods of nested fractions:
1. Multiply top and bottom but the common denominator of top and bottom
2. OR (slower) make one fraction too and bottom, flip and multiply.

13

When canceling terms in the numerator and denominator, always...

Make sure you keep the answer (1) in the numerator for the final answer.

e.g., (a-x) / -xa (a-x) does NOT = -xa

It equals -1/xa! Keep the 1!