Learn on PengiYoshiwara Core MathChapter 3: Measurement

Lesson 3.2: Exponents

In this Grade 8 lesson from Yoshiwara Core Math Chapter 3, students learn exponential notation, including how to identify the base and exponent, write repeated multiplication as a power, and evaluate expressions such as 2 to the fifth or 3 to the fifth. The lesson covers squaring and cubing numbers in the context of area and volume, and connects exponent skills to the Pythagorean theorem. Students practice with whole numbers, fractions, and decimals to build fluency with powers and avoid common mistakes like confusing exponents with multiplication.

Section 1

πŸ“˜ Exponents

New Concept

Exponents are a powerful shorthand for repeated multiplication. In this lesson, we'll master this notation to calculate powers, find areas and volumes, and explore the famous Pythagorean theorem, which connects the sides of a right triangle.

What’s next

Now, let’s dive into worked examples. You'll soon apply these concepts with interactive practice cards and solve challenge problems on the Pythagorean theorem.

Section 2

A New Notation

Property

An exponent is a number that appears above and to the right of a particular factor. It tells us how many times that factor occurs in the product. The factor to which the exponent applies is called the base, and the product is called a power of the base. For example, we can write 32 as 252^5.

Examples

  • "Four to the third power" is written as 434^3. We evaluate it by calculating 4β‹…4β‹…4=644 \cdot 4 \cdot 4 = 64.
  • The repeated multiplication 8β‹…8β‹…8β‹…8β‹…88 \cdot 8 \cdot 8 \cdot 8 \cdot 8 can be written using an exponent as 858^5.

Section 3

Squares and Cubes

Property

The exponents 2 and 3 are used frequently, so they have special names.

  • Instead of reading 525^2 as "5 raised to the second power," we say "5 squared."
  • Instead of reading 535^3 as "5 raised to the third power," we say "5 cubed."

Section 4

Powers Before Products

Property

Rule: Compute powers before multiplications or divisions.
If we want to multiply before computing the power, we must use parentheses around the product. The parentheses tell us to simplify what’s inside first.

Examples

  • To simplify 5β‹…235 \cdot 2^3, you first compute the power 23=82^3=8. Then you multiply: 5β‹…8=405 \cdot 8 = 40.
  • To simplify (5β‹…2)3(5 \cdot 2)^3, you first multiply inside the parentheses 5β‹…2=105 \cdot 2=10. Then you compute the power: 103=100010^3 = 1000.

Section 5

Pythagorean Theorem

Property

A triangle in which one of the angles is a right angle, or 90∘90^\circ, is called a right triangle. The side opposite the right angle is the longest side, called the hypotenuse. The other two sides are the legs.

If cc stands for the length of the hypotenuse, and the lengths of the two legs are aa and bb, then:

a2+b2=c2a^2 + b^2 = c^2

In words: In a right triangle, the sum of the squares of the two legs is equal to the square of the hypotenuse.

Examples

  • A right triangle has legs of length 3 cm and 4 cm. To find the hypotenuse cc, we use 32+42=c23^2 + 4^2 = c^2. This gives 9+16=259 + 16 = 25, so c2=25c^2=25, and the hypotenuse is 5 cm.

Book overview

Jump across lessons in the current chapter without opening the full course modal.

Continue this chapter

Chapter 3: Measurement

  1. Lesson 1

    Lesson 3.1: Volume and Surface Area

  2. Lesson 2Current

    Lesson 3.2: Exponents

  3. Lesson 3

    Lesson 3.3: Units of Measure

  4. Lesson 4

    Lesson 3.4: Circles and Spheres

  5. Lesson 5

    Lesson 3.5: Large Numbers

Lesson overview

Expand to review the lesson summary and core properties.

Expand

Section 1

πŸ“˜ Exponents

New Concept

Exponents are a powerful shorthand for repeated multiplication. In this lesson, we'll master this notation to calculate powers, find areas and volumes, and explore the famous Pythagorean theorem, which connects the sides of a right triangle.

What’s next

Now, let’s dive into worked examples. You'll soon apply these concepts with interactive practice cards and solve challenge problems on the Pythagorean theorem.

Section 2

A New Notation

Property

An exponent is a number that appears above and to the right of a particular factor. It tells us how many times that factor occurs in the product. The factor to which the exponent applies is called the base, and the product is called a power of the base. For example, we can write 32 as 252^5.

Examples

  • "Four to the third power" is written as 434^3. We evaluate it by calculating 4β‹…4β‹…4=644 \cdot 4 \cdot 4 = 64.
  • The repeated multiplication 8β‹…8β‹…8β‹…8β‹…88 \cdot 8 \cdot 8 \cdot 8 \cdot 8 can be written using an exponent as 858^5.

Section 3

Squares and Cubes

Property

The exponents 2 and 3 are used frequently, so they have special names.

  • Instead of reading 525^2 as "5 raised to the second power," we say "5 squared."
  • Instead of reading 535^3 as "5 raised to the third power," we say "5 cubed."

Section 4

Powers Before Products

Property

Rule: Compute powers before multiplications or divisions.
If we want to multiply before computing the power, we must use parentheses around the product. The parentheses tell us to simplify what’s inside first.

Examples

  • To simplify 5β‹…235 \cdot 2^3, you first compute the power 23=82^3=8. Then you multiply: 5β‹…8=405 \cdot 8 = 40.
  • To simplify (5β‹…2)3(5 \cdot 2)^3, you first multiply inside the parentheses 5β‹…2=105 \cdot 2=10. Then you compute the power: 103=100010^3 = 1000.

Section 5

Pythagorean Theorem

Property

A triangle in which one of the angles is a right angle, or 90∘90^\circ, is called a right triangle. The side opposite the right angle is the longest side, called the hypotenuse. The other two sides are the legs.

If cc stands for the length of the hypotenuse, and the lengths of the two legs are aa and bb, then:

a2+b2=c2a^2 + b^2 = c^2

In words: In a right triangle, the sum of the squares of the two legs is equal to the square of the hypotenuse.

Examples

  • A right triangle has legs of length 3 cm and 4 cm. To find the hypotenuse cc, we use 32+42=c23^2 + 4^2 = c^2. This gives 9+16=259 + 16 = 25, so c2=25c^2=25, and the hypotenuse is 5 cm.

Book overview

Jump across lessons in the current chapter without opening the full course modal.

Continue this chapter

Chapter 3: Measurement

  1. Lesson 1

    Lesson 3.1: Volume and Surface Area

  2. Lesson 2Current

    Lesson 3.2: Exponents

  3. Lesson 3

    Lesson 3.3: Units of Measure

  4. Lesson 4

    Lesson 3.4: Circles and Spheres

  5. Lesson 5

    Lesson 3.5: Large Numbers