Subtracting Mixed Numbers with Regrouping

Inside the case file

Subtracting mixed numbers with regrouping gets all ten cases in these 4th grade math worksheets, a no prep CSI Mini Mystery Detective pack for the fractions unit. These math activities work for math centers, morning work, small groups and early finishers, and every case has an answer key. It's pirate themed, which makes it an easy pick for Talk Like a Pirate Day.

Regrouping gets six full cases of its own in this pack, moving from thirds and fourths up to tenths and twelfths and then to big whole numbers. The fractions are printed stacked, the way students write them in their books, and every answer keeps its denominator. Students trade one whole for fourths, eighths or twelfths when the top fraction is too small. They match each answer to a suspect and cross that name off, and each page is self-checking.

What's Inside

• Ten one-page pirate detective cases on subtracting mixed numbers, each with an answer key
• A warm-up case with no regrouping
• Six regrouping cases, from thirds and fourths through eighths, tenths and twelfths
• A case that asks students to decide whether to regroup
• Whole numbers minus mixed numbers, such as 6 - 2 3/8
• Two mixed review cases, including answers less than one whole
• A reference page with worked examples of every step
• A contents page, teacher instructions, a detective case log and a certificate of achievement
• 30 black and white pages, ready to print

The Cases

1. The Empty Treasure Chest - a warm-up with no regrouping
2. The Captain's Missing Hook - regrouping thirds, fourths and fifths
3. The Message in a Bottle - regrouping fifths and sixths
4. The Spinning Ship's Wheel - regrouping eighths
5. The Parrot Who Sang - regrouping tenths and twelfths
6. The Captain's Stolen Hat - bigger whole numbers
7. The Cannon Full of Socks - deciding whether to regroup
8. The Buried Cutlass - whole numbers minus mixed numbers
9. The Midnight Fuse - mixed review
10. The Jolly Roger Swap - mixed review with answers less than one whole

When to Use This Resource

The cases start with a warm-up, then regrouping from thirds up to twelfths, then whole numbers minus mixed numbers. You can hand out one at a time once regrouping has been introduced, or pull a single page when a group needs more practice with a particular denominator. The regroup or not case asks students to check the fractions before they subtract. Guided math groups, homework, test prep, sub plans and homeschool lessons are other good uses.

Grade Levels

Written for 4th grade, where students first subtract mixed numbers with like denominators. The big whole number and mixed review cases give confident 4th graders a stretch, and the pack works as a fractions review early in 5th grade, before unlike denominators.

Why Teachers Love Mystery Detectives

• No setup
• Each answer crosses off a suspect
• Six regrouping cases that build step by step
• A pirate mystery with a parrot, a cannon and the Jolly Roger
• Prints clean in black and white

Want more cases like these?

Follow Kiwiland Education to discover more CSI Mini Mystery Detective cases, no-prep math activities, and detective-themed printables for elementary classrooms.

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