right | equilateral | isosceles | scalene |
---|---|---|---|

All the angles of a triangle add up to 180 degrees. |
If a line MEETS another line, the two angles it makes add up to 180
degrees. |
If two lines cross, the angles ACROSS from each other are the
same. |

Adding and subtracting | Multiplying and dividing |
---|---|

Add: move RIGHT along the number line. Subtract: move LEFT <====== SUBTRACT |---|---|---|---|---|---| -2 -1 0 1 2 3 4 ADD ===========> |
If the numbers you are multiplying or dividing have the SAME sign,
then the result is POSITIVE(+). If they have different signs, then the result is NEGATIVE (-) Example 1: -3 x -3 = +9 (same signs) Example 2: -3 x +3 = -9 (different signs) |

Multiply | Divide | Parentheses |
---|---|---|

A letter and a number together means multiply: 3x = 3 times x |
These mean divide: | Things inside parentheses
are done
first: 3x(5 - 2) = 3 x 3 = 9 |

The circle:

Diameter | Circumference | Area |
---|---|---|

D = 2R | C = D | A = R^{2} |

Translating words to expressions: | |||
---|---|---|---|

Word Phrase | Expression | Comment | |

three times a number | 3x | A number next to a variable means multiply | |

half of a number | x/2 | "half of", "third of", "one fifth of" all mean multiply by fractions, or divide by the denominator | |

one minus 3 times a number | 1 - 3x | ||

one less than 3 times a number |
3x - 1 | Tricky! "less than" means subtract from what follows the "less than" | |

a number increased by 5 |
x + 5 | The word "increase" means add | |

a number decreased by 8 |
x - 8 | The word "decrease" means subtract | |

8 more than 5 times a number |
5x + 8 | "more than" means add | |

6 less than 3 times a number |
3x - 6 | "less than" means subtract from what follows the "less than" |

Mean | Mode | Median | Range |
---|---|---|---|

Mean means average: The average of {3,8,4} is: (3+8+4)/3 = 5 |
Mode means the most common: The mode of {2,3,3,8} is 3 |
Median is the one in the middle.
The median of |
The range is the highest - the lowest The range of {2,8,5,4,1} is 8 - 1 = 7 |

Example | Problem | Answer |
---|---|---|

What is the probability of a flipped coin turning up heads? |
because there is 1 head and the coin has 2 sides. | |

What is the probability of pulling, at random, the ace of spades out of a deck of 52 cards? |
because there is only 1 ace of spades and there are 52 cards in the deck. | |

What is the probability of drawing any ace out of a deck of 52 cards? | because there are 4 aces in a deck of 52 cards. | |

What is the probability of drawing a red marble out of a bag containing 2 red marbles and 5 blue marbles? | because there are 2 red marbles and 7 marbles in all. |