Fraction Addition and Subtraction Flashcards

Grade 5 · Math · Flashcards

Practice key vocabulary and fraction problems for adding and subtracting fractions.

Flashcards

Like denominators: Fractions with the same bottom number; add/subtract numerators directly and keep the denominator
Unlike denominators: Fractions with different bottom numbers; must find the LCD before adding or subtracting
Least Common Denominator (LCD): The smallest number that is a multiple of all the denominators in a problem
How to find the LCD of 1/4 and 1/6: List multiples: 4, 8, 12... and 6, 12... The LCD is 12
Renaming a fraction with a new denominator: Multiply both numerator and denominator by the same number; example: 1/3 = 4/12 (multiply by 4)
2/3 + 1/6: 7/6 = 1 1/6; rename 2/3 as 4/6, then 4/6 + 1/6 = 5/6
3/4 - 2/3: 1/12; LCD is 12, rename as 9/12 - 8/12 = 1/12
Improper fraction: A fraction where the numerator is greater than or equal to the denominator, such as 7/4
Converting 7/4 to a mixed number: 1 3/4; 4 goes into 7 once with 3 left over
GCF (Greatest Common Factor): The largest number that divides evenly into both the numerator and denominator; used to simplify fractions
Simplify 10/15: 2/3; GCF of 10 and 15 is 5, so divide both by 5
Adding mixed numbers: 1 1/2 + 2 1/3: 3 5/6; add whole numbers (1+2=3), then fractions with LCD 6 (3/6+2/6=5/6)
Why can't you just add numerators and denominators?: Denominators tell you the size of each piece; adding them would change the size of the pieces, giving a wrong answer