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# Test 2 & 3

### Math for Teachers I

Question | Answer |
---|---|

1-1 correspondence | a pairing of the elements of A with the elements of B so that each element of A corresponds to exactly one element of B, and vice versa. |

set | A collection of objects |

elements or members | the objects of the set |

Mayan | 360s 20s 1-19 |

babylonian | 3600 60 under 60 |

I | 1 |

V | 5 |

X | 10 |

L | 50 |

C | 100 |

D | 500 |

M | 1,000 |

If a number is deficient, it is prime. | FALSE 4 IS DEFICIENT AND NOT PRIME. |

If a number is prime, it is deficient. | True |

If 4|n and 6|n, then 24|n. | FALSE 4|12 AND 6|12 BUT 24 DOESN’T DIVIDE 12. |

If 5|n and 3|n, then 15|n | TRUE |

If a|n, then there is a number b such that a times b = n | TRUE |

1,260 has exactly 6 factors. | FALSE 48 FACTORS |

If n is divisible by 24 it is also divisible by 4 and 6. | TRUE |

561 is a prime number. | FALSE 3|561 |

One is a prime number | FALSE ONE HAS NOT PROPER FACTORS. |

All prime numbers are odd | FALSE TWO IS PRIME AN EVEN. |

If 12|n, then 3|n | TRUE |

To decide if 36 divides a number, you can try 4 and 9. If 4 and 9 divide the number, then 36 divides the number | True |

If n is divisible by 4 and 6 it is also divisible by 24 | FALSE: 4|12 AND 6|12 BUT 24 DOESN’T DIVIDE 12. |

32|4 | FALSE THERE DOES NOT EXIST A WHOLE NUMBER B SUCH THAT 34 • B = 4. |

Every prime number greater than 2 is one more than an odd number | FALSE EVEN |

To determine if a number is divisible by 11, add its digits. If 11|sum, 11|number. | FALSE, CIRCLE EVERY OTHER DIGIT. ADD THE CIRCLED DIGITS. ADD THE OTHER DIGITS. FIND THE DIFFERENCE OF THESE TWO SUMS. IF 11|THIS DIFFERENCE, 11|THE NUMBER. |

GCF (a,b) + LCM (a,b) = a• b. | FALSE, GCF (a,b) • LCM (a,b) = a• b |

Consider 12, 447, 2d2. What digit should "d" be for this number to be divisible by 18. List all possible answers. | 5 |

2. Consider 14, d27, 120. What digit should "d" be for this number to be divisible by 20. List all possible answers | Any digit or 0,1,2,3,4,5,6,7,8,9 |

3. Consider 31, 106, 23d. What digit should "d" be for this number to be divisible by 12. List all possible answers. | 2 |

4. Consider 12, 447, 2d2. What digit should "d" be for this number to be divisible by 24. List all possible answers. | Since d must be 3 or 7 to pass the 8 rule, and neither of these will result in a sum of digits that is divisible by 3, the answer is: NO POSSIBLE DIGIT. |

Show that you know the process for determining if 214,516,318,199 is divisible by 11. | Sum of circled digits = 2 + 4 + 1 + 3 + 8 + 9 = 27 Sum of other digits = 1 + 5 + 6 + 1 + 1 + 9 = 23 27 – 23 = 4 Since 11 does not divide 4 it does not divide the given number. |

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