Subtraction with Models
Using eighths, rewrite 1/4.
2/8
1/2 − 1/3 = ?
1/6
Is 3/4 − 1/2 closer to 0 or ½?
≈ ¼ → closer to 0
7 3/8 − 4 = ?
3 3/8
A bottle has 3/4 L of water. You drink 1/3. How much remains?
5/12
Using models, compute: 5/8 − 1/4 = ?
3/8
4/5 − 1/6 = ?
19/30
Estimate: 8/9 − 1/12 ≈ ?
1 – 0 = 1
5 3/4 − 2 1/4 = ?
3 1/2
A board is 5 1/2 feet long. You cut off 2 1/4 feet. Remaining?
3 1/4
Which is larger in size: 1 fourth or 2 eighths?
They are equal.
7/8 − 1/12 = ?
21/24 - 2/24 = 19/24
Explain if 11/24 is reasonable for 5/6 − 1/12.
No: 1 – 0 ≈ 1 → 11/24 is about half → not reasonable
8 2/3 − 3 5/6 = ?
LCD = 6 → 5 minus 9/6 = 4 3/6 = 4 1/2
A runner completes 12 2/3 miles on Monday and 9 5/6 miles on Tuesday. How many more miles Monday?
2 5/6
If you line up fraction strips for ¾ and ⅝, which one is longer?
¾
Compute: 11/18 − 5/24 = ?
LCD = 72 → 44/72 − 15/72 = 29/72
Estimate 7 1/2 − 3 1/3
8 – 3 = 5
Borrow to subtract: 6 1/6 − 3 1/2 = ?
5 7/6 − 3 3/6 = 2 4/6 = 2 2/3
A painter has 8 7/8 gallons of paint. He uses 3 3/16. How much left?
5 11/16
A model shows 10 pieces shaded out of 12, then 3 pieces removed. What fraction remains?
7/12
Hard: 17/20 − 3/8 = ?
LCD = 40 → 34/40 − 15/40 = 19/40
Which is the more reasonable difference?
Given: 7/8 − 2/5 =
A) ½
B) 1
A — ½
Hard: 9 5/8 − 4 2/3 = ?
LCD = 24 → 5 + 15/24 − 16/24 = 4 23/24
A baker prepared 14 5/6 trays of cookies. She gives away 7 7/12. How many are left?
LCD = 12 → 14 10/12 - 7 7/12 = 7 3/12 = 7 1/4