This is a free decimal place value, comparing and rounding game for 4th, 5th and 6th grade: a five-minute detective case you put on the board and solve as a class. It practices 4.NF.C.7 (compare decimals to hundredths), 5.NBT.A.3 (read, write and compare decimals) and 5.NBT.A.4 (round decimals). There are no logins, no student accounts and nothing to print unless you want the full case afterwards.
Why it works for decimal place value, comparing and rounding
The badges are decimals like 3.2, 0.45 and 7.08, and the clues are the questions students get wrong in a test: is 0.45 greater than 0.5? What is the tenths digit of 7.08? What does 3.26 round to? The lineup always mixes tenths and hundredths, so the class has to read place value, not just count digits.
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
- Line the six badges up on a place value chart (ones | tenths | hundredths) before the first clue.
- When a clue compares, ask which is bigger, 0.5 or 0.45? and make someone defend the answer.
- Use the rounding clues to catch the habit of rounding the wrong digit. The case explains the rounding when it is solved.
Making it easier or harder
For 4th grade, stay with tenths by tapping New clues until the lineup suits you. For 6th grade, ask students to write the six badges in order first, then play.
Questions teachers ask
What decimals does it use?
Badges from 0.1 to 9.99, a mix of tenths and hundredths. Clues cover comparing, rounding to the nearest whole and tenth, the tenths and hundredths digits and the whole-number part.
Is it good for test review?
It is built for that: five minutes a day in the two weeks before the test, with a different lineup every time.
Is there a printable version?
The packs below are the printable version on the same standards: a page of decimal problems, a lineup of suspects, every right answer crosses one off. Answer keys included.
