Adding & Subtracting Fractions Flashcards

All 8 cards in this deck

How do you add fractions that already have the same denominator?

e.g. $\frac{3}{7}+\frac{2}{7}$

Add the numerators and keep the denominator the same: $\frac{5}{7}$.

What are the steps to add fractions with different denominators?

e.g. $\frac{2}{5}+\frac{1}{4}$

1. Write both with a common denominator: $\frac{8}{20}$ and $\frac{5}{20}$
2. Add the numerators, keeping the denominator: $\frac{13}{20}$

True or false? $\frac{1}{2}+\frac{1}{3}=\frac{2}{5}$ because you add the numerators and add the denominators.

False.

You must use a common denominator: $\frac{3}{6}+\frac{2}{6}=\frac{5}{6}$.

What fraction must be added to $\frac{2}{7}$ to make 1?

$\frac{5}{7}$, because 1 whole is $\frac{7}{7}$.

What are the steps to subtract mixed numbers when the fraction parts need borrowing?

e.g. $3\frac{1}{5}-1\frac{2}{3}$

1. Convert both to improper fractions: $\frac{16}{5}-\frac{5}{3}$
2. Use a common denominator: $\frac{48}{15}-\frac{25}{15}$
3. Subtract the numerators and convert back: $\frac{23}{15}=1\frac{8}{15}$

What are the steps to add mixed numbers without converting to improper fractions?

e.g. $2\frac{1}{4}+1\frac{1}{2}$

1. Add the whole numbers: $2+1=3$
2. Add the fractions using a common denominator: $\frac{1}{4}+\frac{2}{4}=\frac{3}{4}$
3. Combine: $3\frac{3}{4}$

What are the steps to subtract fractions with different denominators?

e.g. $\frac{5}{6}-\frac{1}{4}$

1. Write both with a common denominator: $\frac{10}{12}-\frac{3}{12}$
2. Subtract the numerators only: $\frac{7}{12}$
3. Simplify if possible: $\frac{7}{12}$

What are the steps to subtract mixed numbers when the first fraction part is too small to subtract from?

e.g. $3\frac{1}{5}-1\frac{2}{3}$

1. Use a common denominator: $3\frac{3}{15}-1\frac{10}{15}$
2. Borrow 1 from the whole as $\frac{15}{15}$: $3\frac{3}{15}=2\frac{18}{15}$
3. Subtract wholes then fractions: $1\frac{8}{15}$