  Math Tests - mathematics practice questions

Add and subtract fractions with unlike denominators (medium) If the denominators (the bottom numbers) are the same, we just need to add or subtract the numerators (the top numbers).

\$\$5/7+1/7=6/7\$\$
\$\$4/9−3/9=1/9\$\$

If the denominators (the bottom numbers) are different, we need to find the least common denominator. We can do this by following these steps:

\$\$1/4+1/2\$\$

Step 1: Convert fractions to have the same denominator (by multiplying):

\$\$1/4+1/2×2/2=1/4+2/4\$\$
Step 2: Add or subtract the numerators (the top numbers), and write the result over the same denominator (the bottom number).
\$\$1/4+2/4=3/4\$\$

Sometimes is better to divide one of the fractions:

\$\$4/6+2/3={4÷2}/{6÷2}+2/3=2/3+2/3=4/3\$\$

And in some cases you have to multiply or divide both fractions:

\$\$4/7−1/3=4/7×3/3−1/3×7/7=\$\$
\$\$=12/21−7/21=5/21 \$\$

If you are adding/subtracting fractions and whole numbers, you can turn the whole number into a fraction with the same denominator.

\$\$1/5+1=?\$\$
\$\$1=1/1=2/2=3/3=4/4=5/5\$\$
\$\$;→;1/5+5/5=6/5\$\$
\$\$13/3−4=?\$\$
\$\$4=4/1=8/2=12/3;→;13/3−12/3=1/3\$\$