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Grade 3 · Data

Model-railway pieces: read totals and differences from bars

A survey display at a model railway records three category counts: 36 track pieces, 24 track pieces, and 40 track pieces. Change the controls and explain what the animation reveals.

Predict what will happen, press Play, then pause and explain what changed. Every control also works without playback.

Watch the relationship

Paused
Model-railway pieces: read totals and differences from bars. Items represented now: 0. Final total: 100. Largest final count: 40Final counts: 36, 24, 400A0B0CAll three bars use the same vertical scale.
Counts are fictional nonnegative whole numbers. Categories do not overlap, and each observation contributes to exactly one category. All bars start at zero and share one vertical scale.

Starts paused. Play once, pause anywhere, or use Step to inspect the mathematics. Playback stops when this panel leaves the screen.

Make it your experiment

Change one value. Notice what follows.

The controls adjust the model. Numbers below describe the current frame. Decimals are rounded.

Items represented now
0
Final total
100
Largest final count
40

HD animation studio

From experiment to screen.

Present a crisp Canvas scene, save a full-HD image, or capture your model as a silent video.

Understand what you are seeing

The idea behind the motion.

A survey display at a model railway records three category counts: 36 track pieces, 24 track pieces, and 40 track pieces. A bar graph compares category counts using a common baseline and a common vertical scale. The height represents a count; the width of a bar is decoration and does not represent another variable. The largest final category has 40, the smallest has 24, and all categories together contain 100.

A relationship to keep

Total = 36 + 24 + 40 = 100

Read the symbols alongside the explanation. A diagram shows the relationship; the assumptions tell you when it applies.

  1. STEP 1

    Read the starting situation

    A survey display at a model railway records three category counts: 36 track pieces, 24 track pieces, and 40 track pieces. Identify what each number measures before changing a control; the worked example refers to these starting values.

  2. STEP 2

    Follow the mathematical change

    Advance the timeline to add the observations to their three categories. Compare the live counts, then inspect the final bar heights on the shared scale. Pause on an intermediate frame and compare the picture with the live readouts.

  3. STEP 3

    Explain and test the relationship

    The largest final category has 40, the smallest has 24, and all categories together contain 100. Change one input, predict its effect, and test whether the same relationship still works.

Your turn to explain

Make a prediction. Test your reasoning.

Model-railway pieces: use the original situation. A survey display at a model railway records three category counts: 36 track pieces, 24 track pieces, and 40 track pieces. How many observations separate the largest and smallest final categories?

Use the values specified in the question. Reset restores the initial values for this investigation.

Compare your explanation

16 observations, found by subtracting 24 from 40. The sum answers a different question.

Work through a full lesson

Connect the animation to a worked example and practice questions.

Grade 3 · Statistics

Reason with a larger graph scale

Find differences and totals from a graph using a four-unit scale.