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Spot Decimal-Point and Unit Errors

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A Peek Beyond the Point · Misleading decimal notation · 3:24

You'll learn: A misplaced point or a mixed unit changes a value by a factor of ten or more; check both.

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Spot Decimal-Point and Unit Errors

3:24

Playing

Spot Decimal-Point and Unit Errors

You'll learn: A misplaced point or a mixed unit changes a value by a factor of ten or more; check both.

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Same topic

Misleading decimal notation

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Why 1.5 Hours, 5.6 Feet and 4.3 Overs Can Mislead
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Why 1.5 Hours, 5.6 Feet and 4.3 Overs Can Mislead
You'll learn: Clock time, feet and inches, and cricket overs group by 60, 12 and 6, not 10, so writing them with a dot like a decimal misleads.

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Simple fractions as decimals

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Write Halves, Quarters and Fifths as Decimals
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Write Halves, Quarters and Fifths as Decimals
You'll learn: Rewrite halves, quarters and fifths with denominators 10 or 100 to get their decimals.
Separate a Decimal's Whole and Fractional Parts
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Separate a Decimal's Whole and Fractional Parts
You'll learn: Every decimal has a whole part and a fractional part separated by the point.

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Letters representing numbers

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How Can a Letter Stand for a Changing or Unknown Number?
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How Can a Letter Stand for a Changing or Unknown Number?
You'll learn: A letter can stand for a quantity that changes or for one we don't know yet.
Describe a Number Relationship with Letters
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Describe a Number Relationship with Letters
You'll learn: Translate a number relationship described in words into an expression with letters.

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Formulas from quantities

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Write a Formula for a Total Cost
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Write a Formula for a Total Cost
You'll learn: Write a formula for total cost as price times quantity.
Express an Age Relationship with a Letter
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Express an Age Relationship with a Letter
You'll learn: Write one person's age in terms of another's using a letter.
Write Perimeter Formulas for Regular Shapes
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Write Perimeter Formulas for Regular Shapes
You'll learn: The perimeter of a regular shape is the number of sides times the side length.

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Calendar and number-grid relationships

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Write Relative Values in a Calendar or Number Grid
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Write Relative Values in a Calendar or Number Grid
You'll learn: Write every cell of a calendar or grid block relative to one cell, using row and column rules.
Why Do the Diagonal Sums Match in a Number Grid?
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Why Do the Diagonal Sums Match in a Number Grid?
You'll learn: Using a letter for one corner shows both diagonal sums are always equal.

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Evaluating algebraic expressions

2

Substitute a Number Without Changing the Expression's Structure
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Substitute a Number Without Changing the Expression's Structure
You'll learn: Replace the letter with a number but keep every operation of the expression unchanged.
How Does an Expression's Value Change with Its Input?
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How Does an Expression's Value Change with Its Input?
You'll learn: Substitute different inputs to see how the value of an expression changes.

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Angles at an intersection

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Why Do Adjacent Angles on a Line Add to 180°?
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Why Do Adjacent Angles on a Line Add to 180°?
You'll learn: Adjacent angles that form a straight line together make 180°.
Why Are Vertically Opposite Angles Equal?
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Why Are Vertically Opposite Angles Equal?
You'll learn: A single equality proof needs the linear-pair deductions to remain visible.

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Geometric facts versus measurements

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Why Does Measuring a Diagram Not Prove a Geometric Fact?
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Why Does Measuring a Diagram Not Prove a Geometric Fact?
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