Rounding to the nearest 100 bingo
Rounding to the nearest 100 bingo uses 99 problems (every multiple of 10 from 10 to 990, rounded to the nearest hundred), whose 11 different answers fill 3x3 cards. The caller reads "50 to the nearest 100", players mark 100. With 30 cards a line falls by call 3, so play for a full card (first one at call 19).
100 | 900 | 1000 |
600 | 300 | 700 |
500 | 200 | 800 |
The caller reads a problem; players mark its answer. 99 problems, 11 answers.
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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
Rounding to the nearest 100 at a glance
| What is called | 99 problems: every multiple of 10 from 10 to 990, rounded to the nearest hundred |
|---|---|
| What is on the cards | 11 answers, from 0 to 1000 |
| Recommended card | 3x3: 9 answers per card |
| Different cards possible | 19,958,400 (11 answers placed in 9 squares) |
| Typical level | Grade 3-4 |
| Problems per answer | 4 to 10 |
Answer key: every rounding to the nearest 100 problem by answer
99 calls, 11 squares. First marked = (99 + 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) |
|---|---|---|---|
| 0 | 10 to the nearest 100, 20 to the nearest 100, 30 to the nearest 100, 40 to the nearest 100 | 4 | 20 |
| 100 | 50 to the nearest 100, 60 to the nearest 100, 70 to the nearest 100, 80 to the nearest 100, 90 to the nearest 100, 100 to the nearest 100, 110 to the nearest 100, 120 to the nearest 100, 130 to the nearest 100, 140 to the nearest 100 | 10 | 9.1 |
| 200 | 150 to the nearest 100, 160 to the nearest 100, 170 to the nearest 100, 180 to the nearest 100, 190 to the nearest 100, 200 to the nearest 100, 210 to the nearest 100, 220 to the nearest 100, 230 to the nearest 100, 240 to the nearest 100 | 10 | 9.1 |
| 300 | 250 to the nearest 100, 260 to the nearest 100, 270 to the nearest 100, 280 to the nearest 100, 290 to the nearest 100, 300 to the nearest 100, 310 to the nearest 100, 320 to the nearest 100, 330 to the nearest 100, 340 to the nearest 100 | 10 | 9.1 |
| 400 | 350 to the nearest 100, 360 to the nearest 100, 370 to the nearest 100, 380 to the nearest 100, 390 to the nearest 100, 400 to the nearest 100, 410 to the nearest 100, 420 to the nearest 100, 430 to the nearest 100, 440 to the nearest 100 | 10 | 9.1 |
| 500 | 450 to the nearest 100, 460 to the nearest 100, 470 to the nearest 100, 480 to the nearest 100, 490 to the nearest 100, 500 to the nearest 100, 510 to the nearest 100, 520 to the nearest 100, 530 to the nearest 100, 540 to the nearest 100 | 10 | 9.1 |
| 600 | 550 to the nearest 100, 560 to the nearest 100, 570 to the nearest 100, 580 to the nearest 100, 590 to the nearest 100, 600 to the nearest 100, 610 to the nearest 100, 620 to the nearest 100, 630 to the nearest 100, 640 to the nearest 100 | 10 | 9.1 |
| 700 | 650 to the nearest 100, 660 to the nearest 100, 670 to the nearest 100, 680 to the nearest 100, 690 to the nearest 100, 700 to the nearest 100, 710 to the nearest 100, 720 to the nearest 100, 730 to the nearest 100, 740 to the nearest 100 | 10 | 9.1 |
| 800 | 750 to the nearest 100, 760 to the nearest 100, 770 to the nearest 100, 780 to the nearest 100, 790 to the nearest 100, 800 to the nearest 100, 810 to the nearest 100, 820 to the nearest 100, 830 to the nearest 100, 840 to the nearest 100 | 10 | 9.1 |
| 900 | 850 to the nearest 100, 860 to the nearest 100, 870 to the nearest 100, 880 to the nearest 100, 890 to the nearest 100, 900 to the nearest 100, 910 to the nearest 100, 920 to the nearest 100, 930 to the nearest 100, 940 to the nearest 100 | 10 | 9.1 |
| 1000 | 950 to the nearest 100, 960 to the nearest 100, 970 to the nearest 100, 980 to the nearest 100, 990 to the nearest 100 | 5 | 16.7 |
Self-check: rounding to the nearest 100 answers
- 30 rounds to 0
- 80 rounds to 100
- 180 rounds to 200
- 320 rounds to 300
- 430 rounds to 400
- 460 rounds to 500
- 640 rounds to 600
- 670 rounds to 700
- 830 rounds to 800
- 910 rounds to 900
- 990 rounds to 1000
Why some rounding to the nearest 100 squares fill first
The 99 problems in rounding to the nearest 100 bingo produce only 11 different answers, 9 problems per answer on average. 9 of the 11 answers are reached by 10 problems each; 0 by 4 problems only.
So squares are not equal: an answer with 10 problems is first marked around call 9.1, one with 4 around call 20. After 25 calls, 100 has a 95% chance of being marked against 69% for 0.
For a fairer game, call one problem per answer (11 calls instead of 99); for practice, calling every problem gives the class more repetitions of the facts behind 100.
How long a rounding to the nearest 100 game lasts
300 simulated rounding to the nearest 100 games (3x3, any line wins): 1 card needed 7 calls (median), 10 cards 4, 30 cards 3, with 8 in 10 games between call 3 and 5.
A class of 30 playing rounding to the nearest 100 bingo uses 3% of the 99 calls per game, so one caller sheet covers about 33 games; 3x3 cards from 11 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 19 calls with 30 cards.
How to play rounding to the nearest 100 bingo in class
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Model one call
Work through 950 to the nearest 100 → 1000 on the board and 580 to the nearest 100 → 600, so everyone sees what a call sounds like and which square it marks.
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Hand out the cards
Print 3x3 rounding to the nearest 100 cards: 9 of the 11 answers (0 to 1000) each, 82% coverage.
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Read the problem, not the answer
Call "580 to the nearest 100", pause, then the next. 0 has only 4 problems, so its square fills late.
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Check every bingo
Read back the called problems; the winner names each answer (950 to the nearest 100 → 1000). 30 cards: first bingo near call 3.
Example calls from this set
Four problems drawn from the rounding to the nearest 100 caller sheet and the square each one marks.
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The caller reads 780 to the nearest 100
Mark 800 (also reached by 750 to the nearest 100, 760 to the nearest 100, 770 to the nearest 100 and 6 more)
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The caller reads 440 to the nearest 100
Mark 400 (also reached by 350 to the nearest 100, 360 to the nearest 100, 370 to the nearest 100 and 6 more)
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The caller reads 100 to the nearest 100
Mark 100 (also reached by 50 to the nearest 100, 60 to the nearest 100, 70 to the nearest 100 and 6 more)
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The caller reads 240 to the nearest 100
Mark 200 (also reached by 150 to the nearest 100, 160 to the nearest 100, 170 to the nearest 100 and 6 more)
Frequently asked questions
How many problems are in rounding to the nearest 100 bingo?
99 problems (every multiple of 10 from 10 to 990, rounded to the nearest hundred), with 11 different answers. The caller sheet lists all 99; the cards show only the answers.
What size card works best for rounding to the nearest 100?
3x3. A card needs 9 different answers and the rounding to the nearest 100 set has 11 (0 to 1000), so a 3x3 card is the largest that fits. That still allows 19,958,400 different cards.
Which answers come up most often?
9 of the 11 answers are reached by 10 problems each (100: 50 to the nearest 100, 60 to the nearest 100, 70 to the nearest 100, 80 to the nearest 100, 90 to the nearest 100 and 5 more), so their squares are first marked around call 9.1 on average; 0 with 4 problems waits until about call 20.
How many calls until someone wins?
In 300 simulated rounding to the nearest 100 games with 30 3x3 cards, the first line was completed after a median of 3 calls; with 10 cards after 4 calls.
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