Learn to add and subtract fractions with the same denominator using visual models. Master fraction operations with baking ingredients and real-world scenarios.
Scenario: You're helping bake cookies! The recipe calls for 3/8 cup of sugar and 2/8 cup of salt. How much dry ingredients do you need in total? Later, you use 5/8 cup of flour from a 1 cup container. How much flour is left?
This is where same-denominator fraction addition and subtraction comes in handy! When fractions have the same denominator, adding and subtracting them is just like working with whole numbers.
When adding fractions with the same denominator, add the numerators and keep the denominator the same.
a/c + b/c = (a + b)/c
Example: 3/8 + 2/8 = 5/8
When subtracting fractions with the same denominator, subtract the numerators and keep the denominator the same.
a/c - b/c = (a - b)/c
Example: 8/8 - 5/8 = 3/8
Use fraction circles to visualize addition and subtraction. Each circle represents a whole, divided into equal parts.
Example: 3/8 + 2/8 = 5/8. Color 3 parts of one circle, then 2 parts of another circle. Count total colored parts: 5 out of 8.
The denominator tells us how many equal parts make a whole. When adding or subtracting, we keep the same "size" of parts.
Example: 1/4 + 2/4 = 3/4. We're working with fourths, so the answer is also in fourths.
The numerator tells us how many parts we have. Add or subtract these numbers just like whole numbers.
Example: 5/6 - 2/6 = 3/6. We had 5 parts, used 2 parts, so 3 parts remain.
Practice with fraction circles:
Solve baking problems:
1. 2/5 + 1/5 = ?
2. 3/7 + 2/7 = ?
3. 4/9 + 3/9 = ?
4. 5/12 + 4/12 = ?
5. 7/8 - 3/8 = ?
6. 6/10 - 2/10 = ?
7. 9/11 - 4/11 = ?
8. 8/15 - 3/15 = ?
9. 3/4 + 1/4 - 2/4 = ?
10. 5/6 - 2/6 + 1/6 = ?
11. 7/8 - 3/8 + 2/8 = ?
12. 4/5 + 2/5 - 1/5 = ?
Wrong: 2/5 + 1/5 = 3/10 (Adding denominators)
Correct: 2/5 + 1/5 = 3/5 (Keep denominator, add numerators)
Wrong: 7/8 - 3/8 = 4/0 (Subtracting denominators)
Correct: 7/8 - 3/8 = 4/8 (Keep denominator, subtract numerators)
When adding or subtracting fractions with the same denominator, keep the denominator the same
Add or subtract only the numerators (the top numbers)
Use visual models like fraction circles to understand the concept
Always check your answer by using visual models or real-world examples