We can solve some real-world problems using addition and subtraction of real numbers.
We use addition when there is an increase in the data.
We use subtraction to find a difference, or when there is a decrease in the data.
Let's see some examples.
Luisa has an overdraft facility authorized by her bank. Her bank balance on Monday was On Tuesday, Luisa decided to withdraw to buy a laptop. What is Luisa's bank balance at the end of the day on Tuesday?
To find Luisa's bank balance at the end of the day on Tuesday, we subtract the amount of money Luisa spent on the laptop from the starting balance, as follows:
Therefore, Luisa's bank balance at the end of the day on Tuesday was
The LB electronic store has $\$ 4\,350.50$ saved in a bank account that has an overdraft facility. The store manager decides to use this facility to make a withdrawal of $\$ 5\,000.00$ to buy some cell phones. What was the store's bank balance after making the withdrawal?
|
a
|
$- \$ 609.50$ |
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b
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$- \$ 511.50$ |
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c
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$- \$ 661.50$ |
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d
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$- \$ 649.50$ |
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e
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$- \$ 592.50$ |
Melina is doing an experiment in her Chemistry class. The experiment consists of determining the freezing point of a liquid. The initial temperature of the liquid was $11^{\circ} \, \textrm{C}.$ If the liquid freezes when the temperature drops by $15.5^{\circ} \, \textrm{C}$ from its initial temperature, what is the freezing point of the liquid?
|
a
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$-3.5^{\circ} \, \textrm{C}$ |
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b
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$-6.5^{\circ} \, \textrm{C}$ |
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c
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$-5^{\circ} \, \textrm{C}$ |
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d
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$-4.5^{\circ} \, \textrm{C}$ |
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e
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$-7^{\circ} \, \textrm{C}$ |
Nazareth is doing an experiment in her Chemistry class. She heated a liquid whose initial temperature was After several minutes, the temperature of the liquid rose by at which point she decided to end the experiment. What was the final temperature of the liquid?
To determine the final temperature of the liquid, we add the change in temperature to the initial temperature of the liquid. This gives
Therefore, the temperature of the liquid at the end of the experiment was
Monica has an overdraft facility with her bank. Her bank balance at the start a certain week was $- \$ 90.70.$ On Friday of that week, Monica received a salary of $ \$ 192.10.$ What is Monica's bank balance after receiving the salary?
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a
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$\$ 103.60$ |
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b
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$\$ 91.80$ |
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c
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$\$ 101.40$ |
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d
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$\$ 95.40$ |
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e
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$\$ 99.60$ |
On a certain day in January, the temperature in New York in the morning was $-2.4^{\circ}\,\textrm{C}.$ At noon, the temperature registered a slight increase of $0.7^{\circ}\,\textrm{C}.$ What was the temperature in New York at noon?
|
a
|
$-2.3^{\circ}\,\textrm{C}$ |
|
b
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$-1.2^{\circ}\,\textrm{C}$ |
|
c
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$-2.1^{\circ}\,\textrm{C}$ |
|
d
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$-1.7^{\circ}\,\textrm{C}$ |
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e
|
$-1.3^{\circ}\,\textrm{C}$ |
The city of Kaspiysk, in Russia, is feet below sea level, while the city of La Plata, in Argentina, is feet above sea level. What is the difference between the elevations of both cities?
To calculate the difference between the elevations of both cities, we must calculate the difference between the city with the highest elevation and the city with the lowest elevation. That is, we must calculate This gives
Ana and Peter are doing an experiment in their Chemistry class. The experiment consists of determining the freezing point of two liquids. The liquid that Ana is experimenting with freezes at $-8^{\circ} \, \textrm{C},$ while Peter's liquid freezes at $-15^{\circ} \, \textrm{C}.$ What is the difference between the two temperatures?
|
a
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$8^{\circ} \, \textrm{C}$ |
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b
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$5^{\circ} \, \textrm{C}$ |
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c
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$4^{\circ} \, \textrm{C}$ |
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d
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$9^{\circ} \, \textrm{C}$ |
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e
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$7^{\circ} \, \textrm{C}$ |
Margaret and Juan like freediving. One day they both went to the sea, and while Juan practiced this extreme sport $13$ meters below sea level, Margaret waited for him in the boat, $2$ meters above sea level. If Juan is below Margaret, how far apart are they from each other?
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a
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$12 \, \textrm{m}$ |
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b
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$16 \, \textrm{m}$ |
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c
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$15 \, \textrm{m}$ |
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d
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$11 \, \textrm{m}$ |
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e
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$14 \, \textrm{m}$ |
In Chicago, the average temperature in December is Then in January, the average temperature decreases by compared to December. Finally, in February, the average temperature increases by compared to the previous month. What is Chicago's average temperature in February?
First, we must determine the temperature in Chicago during the month of January. Since we are told that the temperature decreases on average compared to December, we subtract the variation in temperature from the average temperature in December. This gives
Now we must determine the temperature during the month of February. Since we are told that the temperature increases on average compared to January, we add the variation in temperature to the average temperature of January. This gives
Therefore, the average temperature in Chicago in the month of February is
Susan has an overdraft facility with her bank. Her bank balance at the start of a certain week was $- \$ 50.00.$ On Thursday of that week, Susan received a salary of $ \$ 185.80$ into her bank account, for which she decides to withdraw $ \$ 40$ to buy some medicine. What was Susan's ending balance?
|
a
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$\$ 92.30$ |
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b
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$\$ 98.20$ |
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c
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$\$ 95.80$ |
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d
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$\$ 100.40$ |
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e
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$\$ 103.70$ |
Jennifer is doing a science experiment in her Chemistry class. She takes a liquid with a temperature of $10.1^{\circ} \textrm{C}$ and places it in a refrigerator. After half an hour, she removes the liquid from the refrigerator and places it on a table. She concludes that the temperature decreased by $12.7^{\circ} \textrm{C}.$
After half an hour, Jennifer takes the temperature of the liquid again and finds that the temperature increased by $8^{\circ} \textrm{C}.$ What is the final temperature of the liquid?
|
a
|
$4.9^{\circ} \textrm{C}$ |
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b
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$5.4^{\circ} \textrm{C}$ |
|
c
|
$4.5^{\circ} \textrm{C}$ |
|
d
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$4.1^{\circ} \textrm{C}$ |
|
e
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$3.8^{\circ} \textrm{C}$ |