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Grade 3 · Estimation

Festival lanterns: choose the nearer hundred

A report for a neighborhood festival contains a count of 208 and asks for rounding to the nearest 100. 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
Festival lanterns: choose the nearer hundred. Original value: 208. Rounded value: 200. Absolute rounding difference: 8208 rounds to 200200250300Nearest 100 · midpoint 250The outlined marker keeps the original value visible.
Only nonnegative numbers are used. Midpoint ties round upward. The line is rescaled between adjacent multiples; the moving point represents the estimate rather than a newly measured quantity.

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.

Original value
208
Rounded value
200
Absolute rounding difference
8

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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 report for a neighborhood festival contains a count of 208 and asks for rounding to the nearest 100. Rounding replaces an exact value with a nearby multiple of the selected place. Locate the two neighboring multiples and their midpoint before deciding which neighbor is closer. The rounded value differs from the original by 8. A midpoint tie is rounded to the greater multiple in this investigation.

A relationship to keep

208 rounded to the nearest 100 is 200

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 report for a neighborhood festival contains a count of 208 and asks for rounding to the nearest 100. Identify what each number measures before changing a control; the worked example refers to these starting values.

  2. STEP 2

    Follow the mathematical change

    Keep the original marker in view while its estimate moves toward the chosen endpoint. The original count itself is not being changed. Pause on an intermediate frame and compare the picture with the live readouts.

  3. STEP 3

    Explain and test the relationship

    The rounded value differs from the original by 8. A midpoint tie is rounded to the greater multiple in this investigation. Change one input, predict its effect, and test whether the same relationship still works.

Your turn to explain

Make a prediction. Test your reasoning.

Festival lanterns: use the original situation. A report for a neighborhood festival contains a count of 208 and asks for rounding to the nearest 100. What is the absolute difference between the original count and its rounded report?

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

Compare your explanation

8, found from |208 − 200|. This measures rounding difference, not the number of digits removed.

Work through a full lesson

Connect the animation to a worked example and practice questions.

Grade 3 · Algebra

Round to the nearest hundred

Compare a number's distance to adjacent hundreds.