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ESO Y3 · Mathematics
Powers and roots · Powers

Operations with powers

If you fold a sheet of paper in half 42 times, its thickness would reach the Moon. It seems impossible, but each fold multiplies the thickness by 2: $2^{42}$ is more than four trillion. Powers grow enormously, which is why it is worth knowing how to work with them without calculating them.

Before you start, make sure you know: Powers (2nd ESO)
Before you start, make sure you know: Prime factorisation (2nd ESO)

What is a power?

A power is a repeated multiplication of the same number:

$$\underbrace{2 \cdot 2 \cdot 2 \cdot 2 \cdot 2}_{5 \text{ times}} = 2^5 = 32$$ Diagram of the parts of a power, identifying the base 7, the exponent 3 and the calculation of seven cubed. 7 3 ← exponent: how many times ← base: the number that is repeated 7³ = 7 · 7 · 7 = 343 (read "seven cubed")

Move the sliders: each time the exponent goes up by 1, the result is multiplied by the base. That is why the bars shoot up.

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Write the following repeated multiplications as a power and then calculate their numerical value. Remember that the base is the number being repeated and the exponent…

Write the following repeated multiplications as a power and then calculate their numerical value. Remember that the base is the number being repeated and the exponent indicates how many times it appears.

  1. a) $3 \cdot 3 \cdot 3 \cdot 3$
  2. b) $(-2) \cdot (-2) \cdot (-2)$
  3. c) $10 \cdot 10 \cdot 10 \cdot 10 \cdot 10$
  4. d) $\frac{1}{2} \cdot \frac{1}{2} \cdot \frac{1}{2}$
Solve
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We have a classic Rubik's cube. We know that on each edge (side) there are 3 small pieces. Express using a power how many small pieces make up the whole cube and…

We have a classic Rubik's cube. We know that on each edge (side) there are 3 small pieces.

Express using a power how many small pieces make up the whole cube and calculate the value.

Look at the drawing to help you:

Rubik's cube with 3 pieces on each edge: width 3, depth 3 and height 3 3 3 3
Solve

Product and quotient of powers with the same base

$2^3 \cdot 2^4 = (2 \cdot 2 \cdot 2) \cdot (2 \cdot 2 \cdot 2 \cdot 2) = 2^7$. There are 3 twos and then 4 twos: 7 twos in total. The exponents are added.

$\frac{5^6}{5^2} = \frac{5 \cdot 5 \cdot 5 \cdot 5 \cdot \cancel{5} \cdot \cancel{5}}{\cancel{5} \cdot \cancel{5}} = 5^4$. You cross out as many fives as there are in the denominator. The exponents are subtracted.

Explanatory diagram of the product and quotient of powers with the same base by counting and cancelling repeated factors. · 222 2222 2³ 2⁴ = 2³ · 2⁴ = 2³⁺⁴ = 2⁷ Counting factors: 3 + 4 = 7 twos.
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Use the properties of multiplying powers with the same base to simplify these expressions and leave them as a single power. You do not need to calculate the final…

Use the properties of multiplying powers with the same base to simplify these expressions and leave them as a single power. You do not need to calculate the final result, just express the resulting power.

  1. a) $5^3 \cdot 5^4$
  2. b) $(-3)^2 \cdot (-3)^5$
  3. c) $x^2 \cdot x^6 \cdot x$
  4. d) $10^3 \cdot 10^2 \cdot 10^4$
Solve
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Apply the quotient property (division) of powers with the same base to simplify the following expressions to a single power. Remember to subtract the exponents. a)…

Apply the quotient property (division) of powers with the same base to simplify the following expressions to a single power. Remember to subtract the exponents.

  1. a) $\frac{7^8}{7^3}$
  2. b) $2^{12} : 2^{10}$
  3. c) $\frac{(-4)^5}{(-4)^2}$
  4. d) $\frac{a^6}{a}$
Solve
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Calculate the value of the following powers taking into account the properties of zero exponents and powers of base 1. Be careful with the signs. a) $5^0$ b) $23^1$ c)…

Calculate the value of the following powers taking into account the properties of zero exponents and powers of base 1. Be careful with the signs.

  1. a) $5^0$
  2. b) $23^1$
  3. c) $1^{15}$
  4. d) $(-8)^0$
  5. e) $123^0 + 1^{20}$
Solve

Power of a power and powers with the same exponent

$(3^2)^4 = 3^2 \cdot 3^2 \cdot 3^2 \cdot 3^2 = 3^{2+2+2+2} = 3^8$. Four groups of two threes: the exponents are multiplied.

$2^3 \cdot 5^3 = (2 \cdot 2 \cdot 2)(5 \cdot 5 \cdot 5) = (2 \cdot 5)(2 \cdot 5)(2 \cdot 5) = 10^3$. If the exponent is the same, the bases are multiplied.

Visual diagram that groups factors to illustrate the power of a power and the product of powers with a common exponent. 3 · 33 · 33 · 33 · 3 (3²)⁴ = 3⁸ 2 · 52 · 52 · 5 2³ · 5³ = 10³
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Simplify the following expressions using the power of a power property. Leave your answer as a single power. a) $(3^2)^4$ b) $(x^3)^5$ c) $((-2)^2)^3$ d) $((a^2)^3)^4$

Simplify the following expressions using the power of a power property. Leave your answer as a single power.

  1. a) $(3^2)^4$
  2. b) $(x^3)^5$
  3. c) $((-2)^2)^3$
  4. d) $((a^2)^3)^4$
Solve
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In these cases, the bases are different but the exponents are equal. Apply the corresponding properties to group the bases and express the result as a single power. a)…

In these cases, the bases are different but the exponents are equal. Apply the corresponding properties to group the bases and express the result as a single power.

  1. a) $2^3 \cdot 5^3$
  2. b) $12^4 : 4^4$
  3. c) $(-2)^5 \cdot 3^5$
  4. d) $\frac{20^2}{5^2}$
Solve
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We have a square whose side measures $2^4$ centimeters. 1. Express the perimeter of the square as a single power of base 2 (you do not need to calculate the final…

We have a square whose side measures $2^4$ centimeters.

Square of side 2⁴ cm to calculate its perimeter and areaPERIMETERP = ?AREAA = ?l = 2⁴ cml = 2⁴ cm
  1. Express the perimeter of the square as a single power of base 2 (you do not need to calculate the final number, just the power).

  2. Express the area of the square as a single power of base 2.

Solve

Simplifying with prime factors

When the bases are different, the trick is to break them down into prime factors so that equal bases appear.

Diagram of the process of simplifying powers with composite bases by breaking them down into prime factors. 360 2180 290 245 = 3² · 5 360 = 2³ · 3² · 5 factor tree: divide by primes
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Simplify the following operation and express the result as a single power of base 2. To do this, you will first need to break down into prime factors any bases that are…

Simplify the following operation and express the result as a single power of base 2. To do this, you will first need to break down into prime factors any bases that are not prime numbers:

$$ 16 \cdot 2^5 \cdot 4^3 $$
Solve
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Simplify the following numerical fraction by first factorising the bases into prime factors and then applying the properties of powers: $$ \frac{15^2 \cdot 4^2}{6^3…

Simplify the following numerical fraction by first factorising the bases into prime factors and then applying the properties of powers:

$$ \frac{15^2 \cdot 4^2}{6^3 \cdot 10^2} $$
Solve
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An external hard drive has a storage capacity of 1 TB (Terabyte). Knowing that the approximate equivalences in the binary system are: $1 \text{ TB} = 2^{10} \text{ GB}$…

An external hard drive has a storage capacity of 1 TB (Terabyte). Knowing that the approximate equivalences in the binary system are:

  • $1 \text{ TB} = 2^{10} \text{ GB}$

  • $1 \text{ GB} = 2^{10} \text{ MB}$

If a high-quality photograph takes up $2^4$ MB, how many photographs fit in total on the hard drive? Express the result as a power of base 2.

1 TB × 2¹⁰ 2¹⁰ GB × 2¹⁰ 2²⁰ MB 2⁴ MB Capacidad Total: 2²⁰ MB 2⁴ 2⁴ 2⁴ ... 2⁴ ¿Número de fotos? = 2²⁰ ÷ 2⁴
Solve

Back to the start: If a sheet of paper is approximately $0{,}1$ mm thick, folding it 42 times would give $0{,}1\text{ mm} \cdot 2^{42} \approx 440\,000\text{ km}$, exceeding the $384\,400\text{ km}$ that separate us from the Moon.

Summary

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