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Numbers · Real numbers

Scientific notation

World GDP, public debt, the number of users of a social network or the thickness of a hair: economics and the social sciences also deal with numbers so large or so small that writing them out with all their zeros is a mess. Scientific notation makes them manageable without losing precision.

Before you start, make sure you know: Properties of powers (4th ESO)
Before you start, make sure you know: Scientific notation (3rd ESO)

Mantissa and order of magnitude

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The video of a well-known Spanish streamer has reached $45.200.000$ views in just one week. Express this number of views using standard form and state its mantissa and…

The video of a well-known Spanish streamer has reached $45.200.000$ views in just one week. Express this number of views using standard form and state its mantissa and its order of magnitude.

Solve
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In the Biology lab, a group of students observes that the diameter of a red blood cell is approximately $7,5 \cdot 10^{-6}$ meters. The figure shows the red blood cell…

In the Biology lab, a group of students observes that the diameter of a red blood cell is approximately $7,5 \cdot 10^{-6}$ meters. The figure shows the red blood cell with its diameter measurement.

Red blood cell represented as a circle with its diameter dimensioned: 7,5 · 10⁻⁶ metersd ≈ 7,5 · 10⁻⁶ m

Express this measurement in decimal form (standard notation) and explain which way the decimal point moves and by how many places.

Solve

Converting between decimal and scientific form

Examples of converting large quantities (population and public debt) to scientific notation by moving the decimal point to the left. Spain: 47 400 000 inhab. . = 4,74 · 10⁷ move the decimal point 7 places to the left Debt: 1 575 000 000 000 € = 1,575 · 10¹² €
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State which of the following numbers are correctly written in standard form. If any are not, briefly explain why: a) $0,45 \cdot 10^{8}$ b) $1,02 \cdot 10^{-5}$ c)…

State which of the following numbers are correctly written in standard form. If any are not, briefly explain why:

  1. a) $0,45 \cdot 10^{8}$
  2. b) $1,02 \cdot 10^{-5}$
  3. c) $12,5 \cdot 10^{3}$
  4. d) $9,99 \cdot 10^{12}$
Solve
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A technology company is comparing the size of three electronic components. The sizes are: $A = 3,2 \cdot 10^{-4}$ mm, $B = 1,5 \cdot 10^{-3}$ mm and…

A technology company is comparing the size of three electronic components. The sizes are: $A = 3,2 \cdot 10^{-4}$ mm, $B = 1,5 \cdot 10^{-3}$ mm and $C = 8,9 \cdot 10^{-4}$ mm. Order the components from smallest to largest based on their exponents and mantissas.

Solve
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In a data processing centre of a well-known social network, it is estimated that $2,5 \cdot 10^6$ megabytes (MB) of new information are generated every second. a)…

In a data processing centre of a well-known social network, it is estimated that $2,5 \cdot 10^6$ megabytes (MB) of new information are generated every second.

  1. a) Express in standard form how many gigabytes (GB) are generated in a full day (assume $1 \text{ GB} = 10^3 \text{ MB}$).
  1. b) If each storage hard drive has a capacity of $1,2 \cdot 10^{13}$ bytes, how many hard drives would be needed to store the information of a leap year? (assume $1 \text{ MB} = 10^6 \text{ bytes}$). Give the result to three significant figures.
Solve

Order of magnitude, significant figures and comparison

Diagram of orders of magnitude and significant figures for comparing populations and statistical data. population: 4,7·10⁷ GDP in thousands of €: 1,4·10⁹ 10⁴10⁶10⁸10¹⁰ scale of powers of 10: each mark = ×100
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The mean distance from the Earth to the Sun is approximately $1,5 \cdot 10^{8}$ km. If light travels at a speed of $3 \cdot 10^{5}$ km/s, calculate the time it takes for…

The mean distance from the Earth to the Sun is approximately $1,5 \cdot 10^{8}$ km. If light travels at a speed of $3 \cdot 10^{5}$ km/s, calculate the time it takes for sunlight to reach the Earth, carrying out the operation directly in standard form (remember that $t = \frac{d}{v}$).

d = 1,5 · 10⁸ km Sun Earth v = 3 · 10⁵ km/s t = ?
Solve
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The mass of a suspended dust particle is approximately $7,25 \cdot 10^{-10}$ kg. After one week of operation, an air purifier has captured a total of…

The mass of a suspended dust particle is approximately $7,25 \cdot 10^{-10}$ kg. After one week of operation, an air purifier has captured a total of $4,35 \cdot 10^{-2}$ grams of these particles.

  1. a) Calculate the total number of particles captured by the purifier.
  1. b) If the purifier filter must be changed when it reaches an accumulated mass of $1,5 \text{ decigramos}$, how many more weeks can it operate before requiring maintenance? Express the calculations and the final result in standard form.
Solve

Operating in scientific notation

Visual outline of multiplication in scientific notation: multiplying the mantissas, adding the exponents and a final adjustment to standard form. 3 · 10⁹ · 5 · 10⁻³ = 15 · 10⁶ = 1,5 · 10⁷ mantissas: are multiplied powers: the exponents are added

Multiplying and dividing: the mantissas and the powers of $10$ are operated on separately, adding or subtracting the exponents; at the end the mantissa is adjusted if it falls outside $[1,10)$. Adding and subtracting: you must first make the exponents equal.

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A data server stores music files. Each song occupies an average of $4,5 \cdot 10^{6}$ bytes. If the server has $2 \cdot 10^{4}$ songs stored, how many total bytes of…

A data server stores music files. Each song occupies an average of $4,5 \cdot 10^{6}$ bytes. If the server has $2 \cdot 10^{4}$ songs stored, how many total bytes of music are on the server? Express the final result in standard form.

Solve
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Determine the value of $x$ in each of the following equations so that equivalence in standard form is maintained: a) $345.000 = 3,45 \cdot 10^{x}$ b)…

Determine the value of $x$ in each of the following equations so that equivalence in standard form is maintained:

  1. a) $345.000 = 3,45 \cdot 10^{x}$
  2. b) $0,00007 = 7 \cdot 10^{x}$
  3. c) $12,5 \cdot 10^{4} = 1,25 \cdot 10^{x}$
Solve
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A group of researchers is analysing R&D investment by three world powers. The first invests $4,2 \cdot 10^{11} €$, the second $1,85 \cdot 10^{12} €$ and the third…

A group of researchers is analysing R&D investment by three world powers. The first invests $4,2 \cdot 10^{11} €$, the second $1,85 \cdot 10^{12} €$ and the third $9,7 \cdot 10^{10} €$.

  1. a) Calculate the total investment of the three powers combined, expressing the result in standard form.
  1. b) What percentage of the total is represented by the investment of the power that contributes the least money? Round the percentage to two decimal places.
5 10 15 20 · 10¹¹ € 4,2·10¹¹ 1,85·10¹² 9,7·10¹⁰ Power 1 Power 2 Power 3 Lowest investment
Solve
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In microelectronics, the thickness of an insulating layer in a processor is $4,5$ nanometres ($1 \text{ nm} = 10^{-9} \text{ m}$). If the processor has a total surface…

In microelectronics, the thickness of an insulating layer in a processor is $4,5$ nanometres ($1 \text{ nm} = 10^{-9} \text{ m}$). If the processor has a total surface area of $1,2 \text{ cm}^2$:

  1. a) Express the thickness of the layer in metres using standard form.
  1. b) Calculate the total volume of insulating material used in that processor in cubic metres ($m^3$). Take into account that the volume is the product of the surface area and the thickness.
Solve

Applications in economics and demography

Calculation of GDP per capita in scientific notation: dividing GDP by population and approximate result in euros per inhabitant. GDP per capita = GDP / population GDP = 1,42·10¹² € · population = 4,74·10⁷ inhab. ≈ 29 958 € / inhab.
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Carry out the following combined operations and express the result in standard form, rounding to three significant figures: $$\frac{(3,42 \cdot 10^5) \cdot (2,8 \cdot…

Carry out the following combined operations and express the result in standard form, rounding to three significant figures:

$$\frac{(3,42 \cdot 10^5) \cdot (2,8 \cdot 10^{-8})}{1,2 \cdot 10^{-4} + 5,6 \cdot 10^{-5}}$$
Solve
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A red blood cell has an approximately circular shape with a diameter of $7,5 \cdot 10^{-4} \text{ cm}$. a) Calculate the circumference of the cell in metres. (Use…

A red blood cell has an approximately circular shape with a diameter of $7,5 \cdot 10^{-4} \text{ cm}$.

  1. a) Calculate the circumference of the cell in metres. (Use $\pi \approx 3,1416$).
  1. b) If we could line up end to end all the red blood cells of an adult (approximately $2,5 \cdot 10^{13}$ cells), what distance in kilometres would they cover? Express the result in standard form.
Red blood cell d = 7,5 · 10⁻⁴ cm C = ? m Line of cells N = 2,5 · 10¹³ D = ? km
Solve
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In a nanotechnology laboratory, the mass of a new synthetic particle is being analysed, estimated at $m = 4,25 \cdot 10^{-22}$ grams. However, the measuring instrument…

In a nanotechnology laboratory, the mass of a new synthetic particle is being analysed, estimated at $m = 4,25 \cdot 10^{-22}$ grams. However, the measuring instrument has an absolute error bound of $5 \cdot 10^{-25}$ grams. On the other hand, an astronomer measures the mass of a nearby asteroid as $M = 7,8 \cdot 10^{15}$ kilograms with a relative error of $0,01\%$.

Carry out the following tasks, expressing all results in standard form:

  1. a) Determine the interval of possible values for the mass of the particle $m$ using neighbourhood notation $E(a, r)$.
  1. b) Calculate the relative error bound made in measuring the particle and compare it with the relative error of the asteroid. Give reasons to justify which measurement is more precise.
  1. c) If $1,5 \cdot 10^{24}$ identical particles were combined, what would be the resulting total mass? Consider both the estimated value and the accumulated absolute error.
Solve

Back to the beginning: A human hair is about $0{,}000\,08\text{ m}$ thick; expressed in scientific notation as $8 \cdot 10^{-5}\text{ m}$, we avoid counting zeros to the left and can compare its scale directly with microscopic magnitudes.

Summary

See all the exercises in this section