Because you can't add or subtract fractions that have different denominators. Making them like fractions, by multiplying so the denominators are the same, you can add and/or subtract them.
In fractions, you can NEVER add or subtract
If the fractions have the same denominator, add and subtract the numerators as if the denominators weren't there and put the result over that denominator. Reduce if possible. If the fractions have different denominators, find the LCM of the denominators and convert the fractions to equivalent fractions with like denominators. Then add and subtract the numerators as if the denominators weren't there and put the result over that denominator. Reduce if possible.
No, the denominators have to be the same.
You cannot add or subtract fractions with different denominators. If the denominators are different then you need to work with equivalent fractions.
Because you can't add or subtract fractions that have different denominators. Making them like fractions, by multiplying so the denominators are the same, you can add and/or subtract them.
In fractions, you can NEVER add or subtract
If the fractions have the same denominator, add and subtract the numerators as if the denominators weren't there and put the result over that denominator. Reduce if possible. If the fractions have different denominators, find the LCM of the denominators and convert the fractions to equivalent fractions with like denominators. Then add and subtract the numerators as if the denominators weren't there and put the result over that denominator. Reduce if possible.
The same way you would add or subtract whole numbers, leaving the denominators alone.
Because to add fractions, the denominators must be equal.
No, the denominators have to be the same.
Whether the denominators are common or not.
To add and subtract fractions, you need common denominators. To find the common denominator, find the LCM of the denominators you wish to add or subtract.
When you add or subtract fractions with like denominators, you just add or subtract the numerators and put them over the same denominator. For example, 3/5 - 2/5 = (3 - 2)/5 = 1/5
You cannot add or subtract fractions with different denominators. If the denominators are different then you need to work with equivalent fractions.
Possible reasons: To add or subtract fractions, To compare fractions with different denominators.
The denominators must be the same before you can add or subtract fractions.