This week we will shift our focus from multiplication and division to addition and subtraction of fractions.
Yesterday we began with adding and subtracting fractions with like denominators. I like to compare adding and subtracting fractions with like denominators to combining like terms. I used the following example in class
If I have 5 apples and add 3 apples, how many apples to I have?
Answer: 8 apples
We can look at fractions with like denominators the same way
If I have 5/10 (five tenths) and I add 3/10 (3 tenths), how many tenths do I have?
Answer: 8/10 (eight tenths)- this can then be simplified to 4/5
I added the numerators, but I do not change the denominators when adding or subtracting fractions with like denominators. Just like when I added 5 apples and 3 apples, the apples did not change, I just have more of them
We did an activity in class where students used graph paper to represent parts of a whole by drawing and shading a given number of boxes to. The parts of the whole that they shaded represents a fraction that was added or subtracted from another fraction.
Today (Tuesday), we will begin adding and subtracting fractions with different denominators. In this case, we must first find a common denominator and rewrite the original fractions as equivalent fractions with common denominators. Once they are rewritten as equivalent fractions with a common denominator, we can add or subtract the numerators and the denominators stay the same. Below are the steps that we are using in class
1.) Convert any mixed numbers to improper fractions
2.) Find a common denominator (LCM of denominators)
3.) Rewrite original fractions as equivalent fractions with a common denominator (multiply top by same # as bottom)
4.) Add or subtract numerators, denominators stay the same
