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ESO Y4A · Mathematics
Numbers · Integers, rational and decimal numbers

Whole numbers (integers)

Temperatures below zero, overdrawn accounts, ocean depths, years before Christ: these are all integers. You already know how to work with them; here we quickly review the mechanics and put them to work in situations with several steps.

Before you start, make sure you know: Operations with integers (2nd ESO)
Before you start, make sure you know: Operations with powers (3rd ESO)

Combined operations with integers

Step-by-step order of operations for solving a combined operation with square brackets, round brackets, multiplication and division. 5 − [3 − (−4+7)·2] + (−8):4 1st brackets 2nd square brackets 3rd division 4th addition and subtraction
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Evaluate the following combined operation respecting the order of operations: $5 - [ 3 - ( -4 + 7 ) \cdot 2 ] + (-8) : 4$

Evaluate the following combined operation respecting the order of operations:

$5 - [ 3 - ( -4 + 7 ) \cdot 2 ] + (-8) : 4$

Solve
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Work out the following combined calculation, paying special attention to square brackets and powers with negative bases: $12 - [(-2)^3 + 5 \cdot (-3)] : (-1) + (-4)^2$

Work out the following combined calculation, paying special attention to square brackets and powers with negative bases:

$12 - [(-2)^3 + 5 \cdot (-3)] : (-1) + (-4)^2$

Solve

Absolute value

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Work out the numerical value of the following expression containing absolute values: $|-15 + 8| - |3 - 9| + |-2|$

Work out the numerical value of the following expression containing absolute values:

$|-15 + 8| - |3 - 9| + |-2|$

Solve

Powers with a negative base

Diagram of the sign rule for powers according to the parity of the exponent and the presence or absence of brackets even exponent→ + odd exponent→ −
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Determine the sign and work out the exact value of the following powers of integers: $(-2)^4$ $(-3)^3$ $-5^2$ $(-1)^{15}$

Determine the sign and work out the exact value of the following powers of integers:

  • $(-2)^4$

  • $(-3)^3$

  • $-5^2$

  • $(-1)^{15}$

Solve

Integers in context: going up and down, gaining and losing

Any change with two opposite directions (rises/falls, gains/loses, deposits/payments) is modelled with integers: one direction is positive and the other negative.

Vertical diagram of successive descents and ascents that calculates the final depth reached below sea level. 0 m goes down 45 m goes down 120 m goes up 85 m goes down 30 m −45 −120 +85 −30 = −110 m
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An industrial freezer is at a temperature of $-18$ °C. If due to a power failure the temperature rises by $5$ °C and, after repairing it, the motors manage to lower it…

An industrial freezer is at a temperature of $-18$ °C. If due to a power failure the temperature rises by $5$ °C and, after repairing it, the motors manage to lower it by $12$ °C, what is the final temperature of the freezer?

Solve
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The balance of a bank account at the beginning of the month is $-150$ €. Over the course of the week, the following transactions take place: a cash deposit of $400$ €,…

The balance of a bank account at the beginning of the month is $-150$ €. Over the course of the week, the following transactions take place: a cash deposit of $400$ €, an electricity bill payment of $85$ €, an outgoing bank transfer of $230$ € and a maintenance fee charge of $12$ €. Write down the combined calculation and determine the final balance of the account.

Solve
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An underwater drone carries out an ocean exploration. It begins its dive by descending $45$ m from the surface. Then it descends a further $120$ m to investigate a…

An underwater drone carries out an ocean exploration. It begins its dive by descending $45$ m from the surface. Then it descends a further $120$ m to investigate a trench. After taking samples, it ascends $85$ m and stops to photograph a coral. Finally, it descends $30$ m more to return to the sea floor. At what depth is it relative to sea level?

Sea level (0 m) Depth Descends 45 m Descends 120 m Ascends 85 m Descends 30 m ? m
Solve
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In a basketball tournament, the standings are decided by the point difference (difference between points scored and points conceded). In the first four matches, a team's…

In a basketball tournament, the standings are decided by the point difference (difference between points scored and points conceded). In the first four matches, a team's results were: $75-82$, $90-85$, $68-77$ and $85-80$. Express each match's point difference as an integer and work out the team's total point difference at the end of the fourth round.

Solve

Integers with patterns: history and long counts

Historical timeline showing the direct transition from 1 BC to AD 1 to illustrate the absence of a year zero 753 a.C. (there is no 0) 476 d.C. years elapsed between the two dates
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The city of Rome was traditionally founded in $753$ BC and the Western Roman Empire fell in $476$ AD. Given that in the Gregorian historical calendar there is no year…

The city of Rome was traditionally founded in $753$ BC and the Western Roman Empire fell in $476$ AD. Given that in the Gregorian historical calendar there is no year $0$ (it goes directly from $1$ BC to $1$ AD), write an operation using integers to work out exactly how many years passed between both historical events.

Solve
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A computer program modifies a counter $C$ (whose initial value is $C = 0$) using a loop that repeats $100$ times (iterations numbered from $1$ to $100$). On even…

A computer program modifies a counter $C$ (whose initial value is $C = 0$) using a loop that repeats $100$ times (iterations numbered from $1$ to $100$). On even iterations, the program adds $5$ to the counter; on odd iterations, it subtracts $8$. Write an expression using integers that models the process and work out the exact value of the counter $C$ at the end of the $100$ iterations.

Solve

Summary

See all the exercises in this section