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2nd Year · Mathematics
Numbers · Natural numbers

Powers

Aoife posts a video that is shared by $1$ person, and the number of people who have shared it triples every hour. After $5$ hours, writing $3\cdot3\cdot3\cdot3\cdot3$ is tedious and easy to get wrong. That is what powers are for: a short way of writing repeated multiplication.

What a power is

Move the sliders and see how powers grow (or shrink).

Expanded form and standard form

Every place in a number is a power of $10$, so we can write a number in expanded form: $3{,}406 = 3 \cdot 10^3 + 4 \cdot 10^2 + 0 \cdot 10 + 6$.

Very big numbers are written in standard form (also called scientific notation) as $a \times 10^n$ with $1 \le a < 10$.

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Express the following products as a power and state the base and the exponent in each case: a) $5 \times 5 \times 5 \times 5$ b) $12 \times 12 \times 12$ c)…

Express the following products as a power and state the base and the exponent in each case:

  1. a) $5 \times 5 \times 5 \times 5$
  1. b) $12 \times 12 \times 12$
  1. c) $2 \times 2 \times 2 \times 2 \times 2 \times 2$
  1. d) $10 \times 10 \times 10 \times 10 \times 10$
Solve
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Work out the value of the following basic powers: a) $3^{4}$ b) $2^{5}$ c) $7^{2}$ d) $11^{0}$ e) $1^{25}$

Work out the value of the following basic powers:

  1. a) $3^{4}$
  1. b) $2^{5}$
  1. c) $7^{2}$
  1. d) $11^{0}$
  1. e) $1^{25}$
Solve
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Write the polynomial expansion of the following numbers using powers of base $10$: a) $4\,527$ b) $30\,816$ c) $504$

Write the polynomial expansion of the following numbers using powers of base $10$:

  1. a) $4\,527$
  1. b) $30\,816$
  1. c) $504$
Solve
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Express the following data using standard form: a) The mean distance from the Earth to the Moon is about $384\,400$ kilometres. b) The approximate world population is…

Express the following data using standard form:

a) The mean distance from the Earth to the Moon is about $384\,400$ kilometres.

b) The approximate world population is $8\,000\,000\,000$ people.

c) One light-year is approximately equal to $9\,461\,000\,000\,000$ kilometres.

Solve

Multiplying and dividing powers with the same base

Visual justification of adding and subtracting exponents when multiplying and dividing powers with the same base, by expanding their factors 3² · 3⁴ = (3·3)·(3·3·3·3) = 3⁶ add the indices 2 + 4 = 6 7⁵ : 7² = (7·7·7·7·7)/(7·7) = 7³ subtract the indices 5 − 2 = 3
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Apply the laws of indices to write the result as a single power: a) $3^{4} \times 3^{2} \times 3^{5}$ b) $a^{3} \times a^{4}$ c) $10^{2} \times 10 \times 10^{3}$ d)…

Apply the laws of indices to write the result as a single power:

  1. a) $3^{4} \times 3^{2} \times 3^{5}$
  1. b) $a^{3} \times a^{4}$
  1. c) $10^{2} \times 10 \times 10^{3}$
  1. d) $2^{6} \times 2^{6}$
Solve
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Simplify to a single power using the division law of indices for powers with the same base: a) $5^{8} : 5^{3}$ b) $x^{10} : x^{7}$ c) $10^{6} : 10^{5}$ d)…

Simplify to a single power using the division law of indices for powers with the same base:

  1. a) $5^{8} : 5^{3}$
  1. b) $x^{10} : x^{7}$
  1. c) $10^{6} : 10^{5}$
  1. d) $\dfrac{2^{9}}{2^{4}}$
Solve
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Apply the laws of indices to simplify the following expressions to a single power: a) $2^5 \times 2^3 \times 2 =$ b) $(3^4)^3 : 3^7 =$ c) $\frac{5^8 \times 5^2}{5^7} =$

Apply the laws of indices to simplify the following expressions to a single power:

a) $2^5 \times 2^3 \times 2 =$

b) $(3^4)^3 : 3^7 =$

c) $\frac{5^8 \times 5^2}{5^7} =$

Solve

Power of a power, of a product and of a quotient

Visual justification of multiplying exponents in a power of a power, by expanding the factors (4³)² 4^(3 × 2) multiply the indices: 3 × 2 = 4⁶ = 4,096

Powers and roots follow the order of operations (BIMDAS): brackets first, then indices and roots, then multiplication and division, then addition and subtraction.

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Simplify the following expressions, leaving the result as a single power: a) $(4^{3})^{2}$ b) $(10^{5})^{4}$ c) $(x^{2})^{8}$

Simplify the following expressions, leaving the result as a single power:

  1. a) $(4^{3})^{2}$
  1. b) $(10^{5})^{4}$
  1. c) $(x^{2})^{8}$
Solve
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In a logistics warehouse, boxes are organised into cubic shelving units. A storage block consists of 4 shelving units in width, 4 in length, and 4 in height. If each…

In a logistics warehouse, boxes are organised into cubic shelving units. A storage block consists of 4 shelving units in width, 4 in length, and 4 in height. If each shelving unit contains 4 boxes:

a) Express the total number of boxes as a single power.

b) If each box contains $2^3$ packs of paper, how many packs of paper are there in total in the block? Express the result as a power of base 2.

4 4 4 1 SHELVING UNIT ↳ 4 boxes ↳ 1 box = 2³ pkts.
Solve
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Work out the value of the following combined expressions respecting the order of operations: a) $2^4 - 3^2 + \sqrt{25} \times 2 =$ b) $(5-2)^3 + 10^2 : (2^2 + 1) =$ c)…

Work out the value of the following combined expressions respecting the order of operations:

a) $2^4 - 3^2 + \sqrt{25} \times 2 =$

b) $(5-2)^3 + 10^2 : (2^2 + 1) =$

c) $2 \times (3^2 - 4) + \sqrt{64} : 2^3 =$

( ) 1st Brackets xⁿ √ 2nd Powers & Roots · : 3rd Mult. & Div. + - 4th Add. & Subtr.
Solve
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A square mosaic made of square tiles is to be designed. It is known that the number of tiles used is the solution to the following operation: $$ \sqrt{10^2 - 8^2} \times…

A square mosaic made of square tiles is to be designed. It is known that the number of tiles used is the solution to the following operation:

$$ \sqrt{10^2 - 8^2} \times (3^3 - 5^2)^2 - 2^3 $$
  1. a) How many tiles will the mosaic have in total?
  2. b) How many tiles will there be along each side of the square mosaic?
Solve

Finding an unknown index

If you can make both sides of an equation have the same base, you can compare the indices directly.

The same idea works with prime factorisations: for numbers written as products of prime powers, the HCF takes the smaller index of each prime and the LCM takes the larger one.

Three-step procedure for finding an unknown index by reducing to powers of base 2 and equating indices 2ⁿ · 2³ · 2 = 1024 everything in base 2: 2^(n+4) = 2¹⁰ n+4=10 → n=6
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A video by a streamer has gone viral on a social network. During the first few hours, the number of people sharing the video triples every hour. If 3 people shared it at…

A video by a streamer has gone viral on a social network. During the first few hours, the number of people sharing the video triples every hour. If 3 people shared it at the start:

a) Write as a power the number of people who will have shared the video after 5 hours.

b) Work out the value of this power to find the total number of people at that time.

×3 ×3 ... t = 0 h 3¹ N = 3 t = 1 h 3² N = 9 t = 2 h 3³ N = 27 t = 5 h ? N = ?
Solve
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Find the value of the unknown $n$ in the following equations, applying the laws of indices: a) $2^n \times 2^3 \times 2 = 1024$ b) $5^6 : 5^n = 125$ c)…

Find the value of the unknown $n$ in the following equations, applying the laws of indices:

  1. a) $2^n \times 2^3 \times 2 = 1024$
  2. b) $5^6 : 5^n = 125$
  3. c) $(3^2)^n \times 9 = 3^{10}$
Solve
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A natural number $X$ has the following prime factorization: $X = 2^a \times 3^2 \times 5^b$. It is known that: The greatest common divisor of $X$ and $180$ is…

A natural number $X$ has the following prime factorization: $X = 2^a \times 3^2 \times 5^b$.

It is known that:

  • The greatest common divisor of $X$ and $180$ is $2^2 \times 3^2 \times 5^0$.

  • The least common multiple of $X$ and $180$ is $2^3 \times 3^2 \times 5^1$.

Find the values of the exponents $a$ and $b$ and write the number $X$ in decimal notation. (Hint: $180 = 2^2 \times 3^2 \times 5^1$).

Prime factorizations of X, of 180, of their greatest common divisor and of their least common multiple, with the exponents a and b unknown X = 2ᵃ · 3² · 5ᵇ 180 = 2² · 3² · 5¹ GCD = 2² · 3² · 5⁰ LCM = 2³ · 3² · 5¹ (smaller exponents) (larger exponents)
Solve

Back to the start: The number of people who have shared Aoife's video after $5$ hours can be written compactly as $3^5 = 243$.

Summary

See all the exercises in this section