Year 2 Lesson Plan 5 - Fraction addition and perimeter

  1. (5 min) Mental Math
    1. What is 25% of 16? [4]
    2. What is 1/3 of 18? [6]
    3. What is the decimal equivalent of 1/3? [.333...]
    4. What is 2/3 + 2/3? Express your answer as a mixed number [1 1/3]
    5. What is 1/2 of 1/4? [1/8]
    6. What is 50% of 1/2? [1/4 or .25]


  2. (5 min) Review of selected problems from lesson 4 (no more than 3 problems)

  3. (5 min) Review of fractions:

    1. Mixed number conversion to improper fractions: Examples:
          1 1/2 = 3/2         2 1/3 = 7/3        3 1/4 = 13/4
 Ask: How many halves   How many thirds    How many fourths
      are in 1 1/2?     are in 2 1/3?      are in 3 1/4?
      [3]               [7]                [13]
    2. Common denominators: Examples:

      1. 2/3 + 2/5:
        Find a number that both denominators divide into: 3 x 5 = 15
        Multiply 2/3 top and bottom by 5 = 10/15
        [Reason: to make the new denominator 15]
        Multiply 2/5 top and bottom by 3 = 6/15
        Add: 10/15 + 6/15 = 16/15 or 1 1/15.
      2. 1/4 + 5/6
        Ask the class:
        What denominator should we use?
        What do we multiply 1/4 by?
        what do we multiply 5/6 by?
  4. (10 min) Discuss perimeter [length around the edge of a figure].
    1. Use this example:
    2. Discuss perimeter of various shapes:
      1. Perimeter of a square with sides 5 cm [P=20 cm]
      2. Perimeter of an equilateral triangle with sides 5 cm [P= 15 cm]
      3. Perimeter of an isoceles triangle with sides 3,3,4 cm [P= 10 cm]
      4. Circumference of circle with diameter 5 cm [= pi X diameter = 15.7 cm]
      5. Perimeter of regular hexagon with sides 5 cm [P= 30 cm]
        (hex = six)
      6. Perimeter of regular octagon with sides 5 cm [P= 40 cm]
        (oct = 8 [think: octopus])
      7. Perimeter of regular pentagon with sides 5 cm [P= 25 cm]
        (penta = 5 [think Chrysler symbol])
  5. (Remainder of class) In-class exercise

  6. Hand out homework as students successfully complete the in-class exercise.