Halves of even numbers to 20 bingo
Halves of even numbers to 20 bingo uses 10 problems (half of every even number from 2 to 20), whose 10 different answers fill 3x3 cards. The caller reads "half of 6", players mark 3. With 30 cards a line falls by call 3, so play for a full card (first one at call 9).
6 | 1 | 4 |
7 | 3 | 10 |
8 | 2 | 5 |
The caller reads a problem; players mark its answer. 10 problems, 10 answers.
Free: up to 30 different cards per set. Pro: up to 1,000.
Free sets stop at 30 different cards. Your 30 cards are ready to print or download now.
Pro ($19 one-time) opens soon: up to 1,000 different cards per set and 2 or 4 cards on a PDF page. No payment is taken now.
Caller sheet
Every call in a shuffled order. Tick each one as you read it out; the same share link always gives the same order.
Updated
Halves of even numbers to 20 at a glance
| What is called | 10 problems: half of every even number from 2 to 20 |
|---|---|
| What is on the cards | 10 answers, from 1 to 10 |
| Recommended card | 3x3: 9 answers per card |
| Different cards possible | 3,628,800 (10 answers placed in 9 squares) |
| Typical level | Grade 1-2 |
| Problems per answer | one each |
Answer key: every halves of even numbers to 20 problem by answer
10 calls, 10 squares. First marked = (10 + 1) ÷ (problems + 1), the average call at which the answer is reached in a shuffled game.
| Answer | Problems the caller reads | Problems | First marked (avg. call) |
|---|---|---|---|
| 1 | half of 2 | 1 | 5.5 |
| 2 | half of 4 | 1 | 5.5 |
| 3 | half of 6 | 1 | 5.5 |
| 4 | half of 8 | 1 | 5.5 |
| 5 | half of 10 | 1 | 5.5 |
| 6 | half of 12 | 1 | 5.5 |
| 7 | half of 14 | 1 | 5.5 |
| 8 | half of 16 | 1 | 5.5 |
| 9 | half of 18 | 1 | 5.5 |
| 10 | half of 20 | 1 | 5.5 |
Self-check: halves of even numbers to 20 answers
- half of 2 = 1, because 1 + 1 = 2
- half of 4 = 2, because 2 + 2 = 4
- half of 6 = 3, because 3 + 3 = 6
- half of 8 = 4, because 4 + 4 = 8
- half of 10 = 5, because 5 + 5 = 10
- half of 12 = 6, because 6 + 6 = 12
- half of 14 = 7, because 7 + 7 = 14
- half of 16 = 8, because 8 + 8 = 16
- half of 18 = 9, because 9 + 9 = 18
- half of 20 = 10, because 10 + 10 = 20
Is halves of even numbers to 20 bingo fair?
In halves of even numbers to 20 bingo each of the 10 answers comes from exactly 1 problem, from "half of 2" (1) to "half of 20" (10), so every square on the card has the same chance: an answer is first marked at call 5.5 of 10 on average, and after 3 calls each one has a 30% chance of being marked.
With 10 calls in halves of even numbers to 20 bingo and 9 squares per card, every 3x3 card is full by call 10 at the latest, so the shuffle alone decides who shouts first.
How long a halves of even numbers to 20 game lasts
300 simulated halves of even numbers to 20 games (3x3, any line wins): 1 card needed 5 calls (median), 10 cards 3, 30 cards 3, with 8 in 10 games between call 3 and 4.
A class of 30 playing halves of even numbers to 20 bingo uses 30% of the 10 calls per game, so one caller sheet covers about 3 games; 3x3 cards from 10 answers overlap so much that lines fall almost at once, so play for a full card (all 9 squares) instead, which took a median of 9 calls with 30 cards.
How to play halves of even numbers to 20 bingo in class
-
Show the pairs
Use counters to build half of 18 = 9: the same amount twice (or split in two equal groups). The answers run from 1 to 10.
-
Hand out the cards
Print 3x3 halves of even numbers to 20 cards: 9 of the 10 answers (1 to 10) each, 90% coverage.
-
Read the problem, not the answer
Call "half of 16", pause, then the next. 10 calls, one per answer, so no square has a head start.
-
Check every bingo
Read back the called problems; the winner names each answer (half of 18 → 9). 30 cards: first bingo near call 3.
Example calls from this set
Four problems drawn from the halves of even numbers to 20 caller sheet and the square each one marks.
-
The caller reads half of 6
Mark 3 (the only problem with this answer)
-
The caller reads half of 4
Mark 2 (the only problem with this answer)
-
The caller reads half of 8
Mark 4 (the only problem with this answer)
-
The caller reads half of 20
Mark 10 (the only problem with this answer)
Frequently asked questions
How many problems are in halves of even numbers to 20 bingo?
10 problems (half of every even number from 2 to 20), with 10 different answers. The caller sheet lists all 10; the cards show only the answers.
What size card works best for halves of even numbers to 20?
3x3. A card needs 9 different answers and the halves of even numbers to 20 set has 10 (1 to 10), so a 3x3 card is the largest that fits. That still allows 3,628,800 different cards.
Does any answer come up more often than others?
No. Each of the 10 answers is reached by exactly 1 problem of the 10 (half of 2 gives 1, half of 20 gives 10), so every square has the same chance and is first marked around call 5.5 on average.
How many calls until someone wins?
In 300 simulated halves of even numbers to 20 games with 30 3x3 cards, the first line was completed after a median of 3 calls; with 10 cards after 3 calls.