Science quiz
Prime or composite? Sort the numbers
Only the awkward numbers are here: odd, not ending in 5, between 11 and 99. A number appears and you click prime or composite.
- Format
- Sort into groups
- Items
- 30 to sort
- Limit
- 1:30
- Level
- Medium
- Checked
- 2026.10.03
A fresh 30 of the 36 each time. Today's first round is the same for everyone.
- Items
- 30
- Groups
- 2
- Time limit
- 1:30
- A miss
- Shows the answer, then moves on
- Each number appears in turn. Click its kind, or press its number.
- The groups never move, so the number keys are quick.
- Skip (0) sends a prompt to the back of the queue.
- Pause whenever you like (Esc). The board hides while the clock is stopped.
Click whether each number is prime or composite. The groups appear when you start.
About this quiz
A prime has exactly two factors; a composite number has more. Below 100 the only primes you need to try dividing by are 3 and 7, once the even numbers and the fives are gone.
- The pool holds 36 numbers: 21 primes and 15 composites.
- The classic traps are 51, 57, 87 and 91.
- A miss shows the factors before the next number appears.
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|---|---|---|---|---|---|
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| 02 | Number Venn diagram: 1 to 60 Even, prime, square, triangular: three circles, eight regions and eight numbers from 1 to 60 to place. Click the region where each number belongs. Science / Venn diagram / 8 to place | Science | Venn diagram | 8 | 2026.10.03 |
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