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Exponential Decay
Negative Exponents
Multiplying and Dividing Fractions 4
Evaluating Expressions Involving Fractions
The Cartesian Coordinate System
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FOIL Method
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Addition Property of Equality
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Adding and Subtracting Rational Expressions with Identical Denominators
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Factoring The Difference of 2 Squares
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Using Patterns to Multiply Two Binomials
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Roots of Complex Numbers
Methods for Solving Quadratic Equations
Conics in Standard Form
Solving Quadratic Equations by Using the Quadratic Formula
Simplifying Fractions 2
Exponential Notation
Exponential Growth
The Cartesian Plane
Graphing Linear Functions
The Slope of a Line
Finding Cube Roots of Large Numbers
Rotating Axes
Common Mistakes With Percents
Solving an Equation That Contains a Square Root
Rational Equations
Properties of Common Logs
Composition of Functions
Using Percent Equations
Solving Inequalities
Properties of Exponents
Graphing Quadratic Functions
Factoring a Polynomial by Finding the GCF
The Rectangular Coordinate System
Adding and Subtracting Fractions
Multiplying and Dividing Rational Expressions
Improper Fractions and Mixed Numbers
Properties of Exponents
Complex Solutions of Quadratic Equations
Solving Nonlinear Equations by Factoring
Solving Quadratic Equations by Factoring
Least Common Multiples
Solving Exponential Equations
Solving Linear Equations
Multiplication Property of Equality
Multiplying Mixed Numbers
Multiplying Fractions
Reducing a Rational Expression to Lowest Terms
Literal Numbers
Factoring Trinomials
Logarithmic Functions
Adding Fractions with Unlike Denominators
Simplifying Square Roots
Adding Fractions
Equations Quadratic in Form
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Slopes of Parallel Lines
Simplifying Cube Roots That Contain Variables
Functions and Graphs
Complex Numbers
Multiplying and Dividing Fractions 1
Composition of Functions
Intercepts of a Line
Multiplying Two Numbers with the same Tens Digit and whose Ones Digits add up to 10
Factoring Trinomials
Exponents and Polynomials
Decimals and their Equivalent Fractions
Negative Integer Exponents
Adding and Subtracting Mixed Numbers
Solving Quadratic Equations
Theorem of Pythagoras
Equations 1
Subtracting Fractions
Solving Quadratic Equations by Graphing
Evaluating Polynomials
Angles and Degree Measure
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Multiplying Two Numbers with the same Tens Digit and whose Ones Digits add up to 10

There is a neat little trick for multiplying two numbers with the same tens digit where the ones digits add up to 10. An example of this type of problem is 23 × 27. The tens digit is the same, 2, and the ones digits add up to 10, 3 + 7 = 10. Use the following steps.

  • Multiply the ones digits together. Write the product on the right and use two digits of the answer.
  • Multiply the tens digit times 1 plus the tens digit. Write the product to the left.



23 × 27 =

  • Multiply 3 × 7 = 21. Write 21 to the right.
  • Multiply 2 × (2 + 1) = 2 × 3 = 6. Write 6 to the left. 621.

23 × 27 = 621.



49 × 41 =

  • Multiply 9 × 1 = 9. Remember to use two digits. Since 9 is only one digit in length, write 09 to the right for the answer.
  • Multiply 4 × (4 + 1) = 4 × 5 = 20. Write 20. 2009.

49 × 41 = 2009.


Advanced Trick

This trick also works when their are more than 2 digits in the numbers. For example, to multiply 134 × 136, you conside the “tens digit” to be 13.



134 × 136 =

  • Multiply 4 × 6 = 24. Write 24 to the right.
  • Multiply 13 × (13 + 1) = 13 × 14 = 182. Write 182 to the left. 18224.

134 × 136 = 18224.

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