This three-card game compares 347 to the nearest ten, 347 to the nearest hundred, and the midpoint case 345 to the nearest ten. The corresponding answers are 350, 300, and 350 under the declared nonnegative half-up rule. The HTML activity asks for neighboring multiples, distances, and a prediction, then checks those numbers beside a number line and teacher explanation.
Keep the original number visible
R1 starts with 347 and targets the nearest ten. Its neighboring multiples are 340 and 350. The distances are 347 − 340 = 7 and 350 − 347 = 3, so 350 is nearer.
R2 also starts with 347 but targets the nearest hundred. Now the neighbors are 300 and 400. The distances are 47 and 53, making 300 nearer. Do not reuse R1's rounded result as the original number for R2; each card begins with its stated value.
OpenStax's introduction to whole numbers explains rounding to a specified place. These cards use original values to make the place and distance comparison explicit. The task supports whole integers from zero through 999, with nearest-ten and nearest-hundred targets.
Make the midpoint a separate reason
R3 starts with 345 and targets the nearest ten. The neighbors are still 340 and 350, but the distances are five and five. Neither neighbor is closer.
Under this activity's nonnegative half-up convention, choose the higher multiple, 350. Ask learners to say that the distances tie and the stated rule resolves the tie. "350 is closer" is not the correct explanation for this card.
Keep that convention attached to the game. It is not a general policy for negative numbers, financial rounding, or every software function. An exact multiple stays unchanged, and zero rounded to either supported place remains zero.
Attempt the distances before checking
For each card, enter the lower neighbor, upper neighbor, distance to each, prediction, and a short reason. The key and number line stay hidden until all numeric entries and a short reason are filled. The local checker compares the numeric entries with the current number and place. The teacher reviews the written explanation.
A blank entry remains unanswered; it is not interpreted as zero. That matters especially when the original number is zero. Change the number or target place and the old feedback clears so the current inputs cannot appear beside a previous accepted answer.
The number line marks the original number between equally spaced neighbors and includes text distances. Use the text if the graphic is difficult to inspect. Its endpoints describe the current rounding interval, not a new original number.
Keep practice attempts attached to their cards
There are three supplied cards. Repeating R1 is another attempt at R1, not an additional unique question. The example lets a teacher edit the current original number within the supported range and choose ten or hundred for comparison; it is not a random question generator.
Check the place, neighbors, and reason together. If a learner changes from nearest ten to nearest hundred, ask which neighboring multiples must change before discussing the new prediction. This keeps the activity focused on magnitude rather than a memorized answer.
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Create one complete self-contained US-English HTML rounding practice game. Use an original number-line classroom design, large readable labels, minimum 16px text, and a responsive 360px layout. Include local styles and JavaScript only. No random generation, network, persistence, grading records, or fake downloads.
Provide three preset card buttons: R1 original 347 nearest ten, R2 original 347 nearest hundred, R3 original 345 nearest ten. Support only whole-number originals 0..999 and target places ten or hundred. Show a labeled editable original-number input and place buttons; edits clear previous feedback and numeric learner entries. Cards always reload their own original values, never a previous rounded result.
Ask for blank lower neighbor, upper neighbor, lower distance, upper distance, prediction, and reason. Use a type=button Check action. R1 key is 340/350, distances 7/3, prediction 350. R2 key is 300/400, distances 47/53, prediction 300. R3 key is 340/350, distances 5/5, prediction 350 under the stated nonnegative half-up rule. Explain equal distances as a tie rather than calling the higher value closer.
Render an original equally spaced number line and a complete text equivalent with current bounds and original value. Exact multiples remain unchanged; zero is valid and blank remains unanswered. Reject negative, fractional, nonfinite, and out-of-range originals with stale-result clearing.
Require all five numeric entries and a nonblank reason before Check reveals the numeric key and number line. Check only the numeric values; the teacher reviews the reason. Clearing an answer or reason hides the previous number line. Repeated checks do not create extra items. Reset clears all attempts and returns to R1. Use accessible labeled controls and explicit selectors; no form submission. Return the full HTML file.
Try R1 and R2 side by side in your preparation, then reserve R3 for the midpoint explanation. Preview the HTML in NOS if you want to read the number line and distance checks together. Keep the activity cards and teacher key, and begin the discussion by asking what place each answer refers to.