Four numbers, one of which does not belong with the others. These free printable worksheets ask which one and leave space underneath for the reason, because the reason is the part worth having.
The property is never stated. It might be that three are even and one is odd, three are multiples of ten and one is not, three are two-digit and one is three-digit. A child has to look for what the three share before they can say what the fourth is missing, and that search is a different mental move from anything a page of problems asks for.
Why this sheet works
Written answers are what make it work. "25" is a guess that can be right by accident; "25, because the others are all even" cannot. There is room on every question for a sentence, and marking the sentence rather than the circled number is what turns the page from a puzzle into practice.
How this one works
One question from this sheet, worked through a step at a time.
Which number is the odd one out?
12259872
12259872
12259872
25
Do not hunt for the odd one — hunt for what the OTHERS share. Testing each candidate on its own is testing it against nothing, and that is guessing with extra steps.
Look for a property three of them have: 12, 98, 72 — they are all even.
25 is the one that does not, so it is the odd one out. And being able to SAY the shared property is what makes it an answer rather than a guess.
1. 12, 25, 98, 72 → 25 (the other three are all even)2. 17, 29, 73, 9 → 9 (the other three are all prime numbers)3. 72, 32, 99, 63 → 32 (the other three are all multiples of 9)4. 92, 10, 60, 30 → 92 (the other three are all multiples of 10)
