Read & Watch: Calculating Time
OVERVIEW
On this page, you will learn about using subtraction or addition to calculate time.
- First, read the text about using subtraction or addition to calculate time.
- Then, read and watch the video about how to use the calculator on your computer.
READ & WATCH
Read:
Remember how to say and write a number sentence when you subtract.
Say: four minus two equals two
Write: 4 - 2 = 2
We use subtraction in history to calculate to total number of years. The total can tell us how long something lasted or how many years ago something happened.
Examples:
How many years after the Spanish did the British arrive in Washington?
The Spanish arrived in 1774. The British arrived in 1778.
Subtraction:
1778 is the larger number, so we put that first.
1778 - 1774 = 4
The British arrived four (4) years after the Spanish.
How many years did Vancouver work on his map?
He worked on the map from 1792 to 1794.
Subtraction:
1794 is the larger number, so we put that first.
1794 - 1792 = 2
Vancouver worked on his map for two (2) years.
How many years ago did the Americans arrive in Washington?
Robert Gray arrived in 1792. Now, it is 2016.
Subtraction:
2016 is the larger number, so we put that first.
2016 - 1792 = 224
Robert Gray arrived 224 years ago.
Read:
We can also use addition in history to calculate time.
Remember how to say and write a number sentence when you add.
Say: four plus two equals six
Write: 4 + 2 = 6
Example:
How many years ago did the Americans arrive in Washington?
Robert Gray arrived in 1792. Now, it is 2016.
Start with the smaller number 1792 - add 100 years at a time until you reach 1992 = 200 years (note: 2092 would be too far since it say it is now 2016).
1992 - add 10 years at a time until you get as close to 2016 as possible without going over- you will reach 2012 = 20 years
2012 - add 1 year at a time until you reach 2016 = 4 years
200 + 20 + 4 = 224
Robert Gray arrived 224 years ago.
Read:
There are many tools on a computer. One of those tools is a calculator. You find the calculator in the Start Menu under Accessories.
To use the calculator, you click on the symbol. Calculators help you when you need to do math problems.
| CALCULATOR SYMBOL | WORD |
|---|---|
| + | plus |
| - | minus |
| * | times |
| / | divide by |
| C | clear |
| . | decimal point or point |
| 1, 2, 3 | numbers |
| = | equal sign |
Watch:
USING THE CALCULATOR TOOL
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