This is a free place value and rounding game for 2nd, 3rd and 4th grade: a five-minute detective case you put on the board and solve as a class. It practices 2.NBT.A.1 (hundreds, tens and ones), 3.NBT.A.1 (round to the nearest 10 or 100) and 4.NBT.A.2 (compare multi-digit numbers). There are no logins, no student accounts and nothing to print unless you want the full case afterwards.
Why it works for place value and rounding
The badges are three-digit numbers and the clues are the questions you ask in a place value unit: which digit is in the tens place? What does it round to? Is it greater than 500? The class has to read every badge properly to clear it, and the student who rounds 365 to 300 is found out gently, by the game.
How to run it
- Put it on the board. Tap Put it on the board above the case and it fills the screen. Six suspects, each wearing a badge number. One of them did it.
- Read clue 1 out loud. The class works out which badges the clue rules out. Tap each suspect it clears; a correct tap stamps them CLEARED, a wrong one just wobbles.
- Clues 2 and 3 unlock as you go. Keep clearing until one suspect is left, then tap them to close the case. The reveal explains every clue.
- Play it again. New lineup keeps the clues and shuffles the suspects. New clues gives you a fresh case. Round 2 and Round 3 are waiting in the tabs.
Three tips from the classroom
- Write hundreds | tens | ones on the board and point as you read each clue.
- For rounding clues, ask which two hundreds is it between, and which is it closer to? before anyone taps.
- Let students explain why a badge is cleared, not just tap it. The explanation is the assessment.
Making it easier or harder
For 2nd grade, pause on the rounding clues and do them together. For 4th grade, ask students to write the six badges in order from least to greatest before the first clue.
Questions teachers ask
What numbers does it use?
Three-digit badges from 101 to 999. Clues cover the hundreds, tens and ones digits, rounding to the nearest ten and hundred, digit sums and comparing.
Does it cover rounding to the nearest ten?
Yes, and to the nearest hundred. Both come up, and the case explains the rounding when it is solved.
Is there a printable version?
The packs below are the printable version: a page of place value problems, a lineup of suspects, every right answer crosses one off. Answer keys included.
