## Lesson Plan #21 - Squares, Cubes and Square Roots

1. (5 min) Mental Math
1. What is the probability of flipping a coin twice
and getting a 'heads' both times? [1/4]
2. Start with 2700, divide by 100, then divide by 3 [9]
3. What is the probability of drawing a black 8
out of a deck of 52 cards? [1/26]
4. What is 30% of 90? [27]
5. Multiply 1/3 by 3/4 and reduce [1/4]

2. (5 min) Review of homework #18 (<= 3 problems)

3. (10 min) Introduce squares,cubes and square roots:

1. Pass out the "Squares, Cubes, and Square Roots" handout.
2. Follow the discussion in the handout.
3. Have students fill out the table on the first page of the handout.
4. Follow the "Square Root" discussion on the second page of the handout.
5. Have the students fill out the table on the second page of the handout.
6. Show students the square root key on the calculator. Do a few simple square roots using this key.
7. Discuss the solution of equations with squares:
 Example 1: x2 + 4 = 20 Solution: x = 4 Example 2: 40 - x2 = 4 Solution: x = 6 Example 3: 2x2 - 1 = 17 Solution: x = 3
Have them use the "Cover up" technique they already know to solve these equations.
4. (Remainder of class) In-class Exercise.

5. Hand out homework as students successfully complete the in-class exercise.
 Note: Students have a tendency to compute squares as multiplies by 2:52 = 5 x 2 = 10 This is reinforced by the fact that it works for 2: 22 = 2 x 2 = 4 Watch for this!!