Videos to help Grade 6 students learn what are exponents and how to use exponents

New York State Common Core Math Module 4, Grade 6, Lesson 5

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Common Core For Grade 6

Lesson 5 Student Outcomes

Students discover that 3x = x + x + x is not the same thing as x

Students understand that a base number can be represented with a positive whole number, positive fraction, or positive decimal and that for any number b, we define b

Opening Exercise

As you evaluate these expressions, pay attention to how you arrive at your answers.

4 + 4 + 4 + 4 + 4 + 4 + 4 +4 + 4 + 4

9 + 9 + 9 + 9 + 9

10 + 10 + 10 + 10 + 10

Multiplication is a faster way to add numbers when the addends are the same.

When we add five groups of 10, we use an abbreviation and a different notation, called multiplication.

10 + 10 + 10 + 10 + 10 = 10 × 5 = 50.

If multiplication is a more efficient way to represent addition problems involving the repeated addition of the same addend, do you think there might be a more efficient way to represent the repeated multiplication of the same factor, as in 10 x 10 x 10 x 10 x 10.

When we add 5 groups of 10, we write 5 × 10, but when we multiply 5 copies of 10, we write 10^{5}. So, multiplication by 5 in the context of addition corresponds exactly to the exponent in the context of multiplication.

The repeated factor is called the **base** and the exponent is also called the **power**.

There is a special name for numbers raised to the second power. When a number is raised to the second power, it is called **squared**.

There is also a special name for numbers raised to the third power. When a number is raised to the third power, it is called **cubed**.

Examples

Write equivalent expressions:

5 × 5 × 5 × 5 × 5

2 × 2 × 2 × 2

8^{3}

10^{6}

g^{3}

2.
What is the difference between 3g and g^{3}?

The base number can be written in decimal or fraction form.

3.8^{4}

(2/3)^{2}

Exercises

1. Fill in the missing expressions for each row. For whole number and decimal bases, use a calculator to find the standard form of the number. For fraction bases, leave your answer as a fraction.

2. Write “five cubed” in all three forms: exponential form, written as a series of products, standard form.

3. Write “fourteen and seven tenths squared” in all three forms.

4. One student thought two to the third power was equal to six. What mistake do you think they made and how would you help them fix their mistake?

Lesson Summary

**Exponential Notation for Whole Number Exponents**: Let be a non-zero whole number. For any number b, the expression b^{m} is the product of m factors of b.

When m is 1, “the product of one factor of ” just means b, i.e. b^{1} = b. Raising any non-zero number to the power of 0 is defined to be 1, i.e., b^{0} = 1 for all b ≠ 0.

Lesson 5 Examples and Exercises

Examples 1 - 5

Go back to Examples 14 and use a calculator to evaluate the expressions.

Example 6

3.8

Example 7

2.1 × 2.1

Example 8

0.75 × 0.75 × 0.75

The base number can also be a fraction. Convert the decimals to fractions in Examples 7 and 8 and evaluate. Leave your answer as a fraction.

Example 9

1/2 × 1/2 × 1/2

Example 10

(2/3)

Exercises 1 - 4

Lesson 5 Exit Ticket

1. What is the difference between 6z and z

2. Write 10

3. Write 8 × 8 × 8 × 8 using exponents.

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