100s Chart Missing Numbers Within 100 Monster Mystery Detective Activity

Inside the case file

Missing numbers to 100 worksheets for 1st grade and 2nd grade, hundreds chart practice built as five monster Mystery Detective math cases, the number before and the number after on every page. Print and go with full answer keys as back to school math activities for August and September, then no prep morning work, math centers, early finishers, homework and sub plans whenever number order slips. Monsters are loose in the school, each number a student writes crosses a suspect off the lineup, and a wrong number matches nobody, so this CSI Mini Mystery Detective set is counting to 100 the way it is tested and marks itself.

The first month of first grade is for finding out who can count past a ten without the chart on the wall, and five monster CSI Mini Mystery Detective math cases do it without anything that looks like a test. A six year old fills the gaps to catch the monster, the lineup tells them when a number is wrong, and one case fits a morning work slot.

The Cases

1. The Student Monster - something is loose in the school
2. Monster Principal - the principal is not himself today
3. Monster Teacher - extra schoolwork for everybody
4. School Imposter Among Us - something got inside the school
5. Monster Thief - every school book has gone

What's Inside

• Five case files, each with a crime sheet and its own lineup of suspects
• Missing numbers to 100, and the numbers that come before and after
• Sequences printed with gaps, the way they appear on a hundreds chart
• Each answer matches one suspect and no other, so the page checks itself
• A full answer key for every case
• 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 carrying one crime and one lineup of suspects. Each suspect has a number, the crime sheet produces those numbers, and a correct answer takes that suspect out until a single name is left. Nothing is laminated, charged or bought, so the math does the whole job, and that is the difference between these detective activities and a page of math worksheets. A case runs about a class period.

When to Use This Resource

Use these while the hundreds chart is still on the wall and you want to know who can work without it. They show you quickly which children lose the sequence when they cross a ten, which is the bit that matters for everything that comes after. The monsters do the work of holding attention, and a wrong number crosses off the wrong suspect so the child spots it themselves.

Teachers use it for test prep, homework, math centers, morning work, early finishers, sub plans and homeschool lessons, with a class, a small group or one child alone.

Grade Levels

Written for 1st grade, where counting and writing numbers to 100 sits in the standards, and used with 2nd graders as a start of year check. Kindergarten classes take it late in the year once they are confident past fifty.

Why Teachers Love These Cases

• Shows you who is counting past a ten and who is guessing
• Students correct themselves as the wrong monster comes off the lineup
• No prep, and the answer keys make grading quick
• Works with a whole class, a small group, partners, or one student alone

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