Missing Numbers to 120 (Before & After)

Inside the case file

Missing numbers to 120 worksheets for 1st grade and 2nd grade: five monster math cases, Mystery Detective pages of writing the number before and the number after. No prep, print and go, full answer keys: morning work, math centers, early finishers, homework and sub plans. A classmate who is not what they seem, a principal taken over and a monster thief who has emptied the library carry the cases; each right number crosses a suspect off the list, counting past 100 is the only way through, and a first grader will count all morning to catch the CSI Mini Mystery Detective thief.

Counting past 100 is where a first grade class stops being able to do it in their heads, and a monster loose in the school is what gets five pages of practice done. A wrong number matches no suspect, so students see the slip themselves, and one case fits a morning work slot. Five math pages from one Mystery Detective download covers the week.

The Cases

1. The Student Monster - one of the class is not what they seem
2. Monster Principal - the principal has been taken over
3. Monster Teacher - and now there is extra homework
4. School Imposter Among Us - somebody has infiltrated
5. Monster Thief - all the school books have gone

What's Inside

• Five case files on the number before and the number after, to 120
• Numbers run past 100, so the class practices the tricky part
• A suspect list beside the questions, so one answer removes one name
• A red-ink answer key for all five cases
• Five separate monster stories, so no two pages read the same
• Print and go: no cutting, no laminating, nothing to prepare

What Is a CSI Mini Mystery Detective?

A CSI Mini Mystery Detective is one printed page with a crime at the top and a lineup of suspects beside the questions. Every suspect carries a number, the answers on the page produce those numbers, and a match takes that name out. The one nobody matched is the culprit. Nothing is cut, laminated or charged, and counting correctly is the only way through.

When to Use This Resource

This belongs in the stretch of first grade where counting to 120 sits in the standards and the class is writing numbers rather than saying them. It is equally useful at the start of second grade as a quick check of what stuck over the summer, and the monster theme makes it an easy pick for October. All the instructions are on the page, so it goes into a sub folder as it is.

Use it for morning work, math centers, early finishers, homework, sub plans and homeschool lessons, with a whole class, a small group or one student.

Grade Levels

Written for 1st grade, where counting and writing numbers to 120 sits in the standards. Second graders use it as a start of year check, and kindergarten classes late in the year once they are confident past fifty.

Why Teachers Love These Cases

• A miscount matches no suspect, so a child spots it without being told
• Nothing to prepare beyond pressing print
• Five short cases covers a week of morning work
• The monsters carry a class that has gone off number lines

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