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Could You Reach the Moon in Ten Years?

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Large Numbers Around Us · Estimation thought-experiments · 3:29

You'll learn: Estimate in stages, distance then speed then time, to test whether the Moon is reachable in ten years.

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Could You Reach the Moon in Ten Years?

3:29

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Could You Reach the Moon in Ten Years?

You'll learn: Estimate in stages, distance then speed then time, to test whether the Moon is reachable in ten years.

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Estimation thought-experiments

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Could a Lakh Buses Hold a City's Population?
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Could a Lakh Buses Hold a City's Population?
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Toothpick-digit exploration

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Make the Largest and Smallest Numbers with Fixed Toothpicks
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Make the Largest and Smallest Numbers with Fixed Toothpicks
You'll learn: Moving a fixed number of toothpicks changes digits; plan moves to make the largest and smallest numbers.

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Expressions and their values

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Turn a Calculation Story into an Arithmetic Expression
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Turn a Calculation Story into an Arithmetic Expression
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Find the Value of an Arithmetic Expression
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Find the Value of an Arithmetic Expression
You'll learn: Evaluate an expression term by term to find its value.

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Comparing expressions through reasoning

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Compare Two Expressions Without Calculating Everything
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Compare Two Expressions Without Calculating Everything
You'll learn: Compare two expressions by tracking how their parts differ, without calculating everything.
Change an Expression While Keeping Its Value
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Change an Expression While Keeping Its Value
You'll learn: Change parts of an expression in balancing ways so its value stays the same.

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Brackets and meaning

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How Do Brackets Change a Calculation's Meaning?
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How Do Brackets Change a Calculation's Meaning?
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Evaluate a Bracketed Expression One Group at a Time
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You'll learn: Evaluate the bracketed groups first, then combine the results.

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Identifying terms

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Rewrite Subtraction as Addition of an Opposite
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Rewrite Subtraction as Addition of an Opposite
You'll learn: Subtracting a number is the same as adding its opposite, which turns expressions into sums of terms.
Identify Whole Terms Before Evaluating an Expression
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You'll learn: Products and quotients form single terms; identify the terms first, then add them.

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Swapping and grouping terms

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Reorder Signed Terms Without Changing Their Value
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Reorder Signed Terms Without Changing Their Value
You'll learn: Signed terms can be added in any order and grouping without changing the value.
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When Does Swapping Numbers Change an Expression?
You'll learn: Swapping numbers inside a subtraction or division changes the value; swapping whole signed terms does not.

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Removing brackets and compensating changes

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Remove Brackets Without Losing the Signs
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Remove Brackets Without Losing the Signs
You'll learn: A minus sign before a bracket flips the sign of every term inside when the bracket is removed.
Subtract 9 by Subtracting 10 and Adding 1
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Subtract 9 by Subtracting 10 and Adding 1
You'll learn: Changing one term changes the total by the same amount, so subtract 10 and add 1 to subtract 9.

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Distribution and expression transformations

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Why Can Multiplication Spread Across a Sum or Difference?
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You'll learn: A number times a sum equals the sum of the separate products, shown with a grid of objects.