Number Detective
A daily number-guessing puzzle for any child who can read digits. Find the secret 3 or 4-digit number using green, gold and grey clues, then share your result.
Find the secret number. No digit is used twice. After each guess, a green tile is the right digit in the right place, a gold tile is in the number but in the wrong place, and a grey tile is not in the number at all.
Number Detective · free from Fieldbook Learning
How to play
Type or tap a number with no repeated digits, then press Guess. Each digit turns green, gold or grey to tell you how close you are. You have eight guesses. There is a new puzzle every day, the same one for everyone, so a family or class can compare. Copy my result shares a row of coloured squares without giving the answer away.
What children practise
- Place value: a digit's position changes what it means, and the tiles show that position matters.
- Logical reasoning: use what the last guess ruled out before making the next one.
- Digits and number sense: 3-digit and 4-digit puzzles, from about Grade 2 up.
Ideas to try
- Play together and take turns choosing the next guess. Say out loud why you chose it.
- Ask: after a guess with no green or gold tiles, which digits can you cross off? How does that help?
- Write the biggest and smallest numbers possible from the digits you have found.
The puzzle is made in your browser. Nothing is saved or sent anywhere.
Free to use, no account needed. It runs in your browser: nothing you type, and no sound from your microphone, is sent to Fieldbook.
Hands-on lessons to pair with Number Detective
Ready-to-teach units, each lesson a printable teacher guide and student sheet. Your first three lessons are free.
Data Detectives
How fast are our reflexes? Which graph is telling the truth? Do taller people really have bigger hands? Three lessons where students collect their own measurements and find out what numbers can and can't tell you.
Evidence Lab
How do you know something is true? Students test a claim with their own measurements, find out why one result is never enough, and learn to tell strong evidence from weak.
Measure It: Length, Time and Mass in the Real World
Whose foot is the right ruler? How long is a minute, really? Is a kilogram of feathers lighter than a kilogram of rocks? Four lessons where students measure length, time and mass with real tools, then use their own data to settle an argument.
Three full lessons, free
Make a free account and download any three Fieldbook lessons, from any grade or subject, as printable PDFs. No card needed.
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