Key Concepts and Ideas For Fractions


Fill in the blanks for the following.  Then come up with an example that illustrates each.  Hold the mouse over the yellow box to check your answer.


  1. The top number of a fraction is called the                                               .

  2. The bottom number of a fraction is called the                                         .

  3. The prime numbers below twenty are 2, 3, 5,                                        .

  4. To reduce a fraction we can cancel out                                      .
    common factors

  5. To change a mixed number to an improper fraction, multiply the
                              by the                           and add it to the                                  .
    whole number, denominator, numerator

  6. When multiplying proper or improper fractions, first                                and then                                              .
    reduce, multiply across

  7. When multiplying a whole number by a fraction, first change the whole number to                                    and then multiply across.
    the denominator over 1

  8. To divide proper or improper fractions, change to a multiplication by multiplying by the                                                  .

  9. When multiplying or dividing mixed numbers, you must first change the mixed numbers to                                                before multiplying across.
    improper fractions

  10. We find the least common denominator (LCD) of two or more fractions by finding the least common multiple of the                                                 .

  11. To find the least common multiple, first write each of the numbers as a product of                                                and then use each prime the                                      number of times it appears in any denominator.
    primes, greatest

  12. To build two fractions, first find the                                 , and then find how many times the                                must be multiplied to get the LCD.  Finally multiply the                                    by this number.
    LCD, denominator, numerator

  13. To add fractions with the same denominators, you get the sumís numerators by                           the two numerators, while the sumís denominator is                                                  .
    adding, the original denominator

  14. To add or subtract proper or improper fractions with different denominators, first find the                        , then                            up the fractions, and finally add the two fractions.
    LCD, build

  15. To add mixed numbers, separately add the                                             parts and the                              parts.  If the sum of the fractional parts produces an improper fraction, change the improper fraction to a                    number.  Then add the 1 to the whole number sum.
    whole number, fractional, mixed

  16. To subtract mixed numbers, separately subtract the                                            parts and the                              parts.  Then build the fractions.  If the first fraction is smaller than the second, then                       1 from the whole number.  Write this 1 as                         over                            .  Finally add and subtract the fractions.
    whole number, fractional, borrow, the denominator, the denominator

  17. The order of operations is                              and              then                       and                  .  If there is a tie, then read                   to                   .
    ( ), exponents, x, /, +, -, left, right


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