## 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
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.