Math 6 High ( Period 3)

Adding & Subtracting Fractions 3.1 

To add fractions with common denominators à just add their numerators ad write this sum over the denominator.

To subtract fractions with common denominators à just subtract their numerators and write the difference over the denominator

1/7 + 3/ 7 = 4/7

7/10 – 3/1-0 = 4/10 = 2/5

In the 2^nd example we found 4/10 to be our answer but then we could simplify… Always simplify your answer.

We then drew the picture on Page 111 of the stack of books and found the height of the stack.

3/8 + 7/8 = 10/8  which is an improper fraction so we changed it to a mixed number 1 ¼  So the books were stacked  1 ¼ in

To add and subtract fractions with different denominators first rewrite the fractions so that they have the SAME denominator. Then use the rules above.

You can use ANY COMMON DENOMINATOR ( the LCD is the Best—but we will discuss that tomorrow in detail)

a/b + c/d = (ad + bc)/bd

If you cannot figure out a common denominator—one of the choices is always to multiply the denominators. That product will always be one of the common denominators!

¼ + 2/ 5 =

1(5) +4(2)
20

13/20