9.04 Measure and estimate lengths
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Do you know what a length is? It is a measure of distance between two points, such as the two ends of an object. This lesson we will look at measuring some lengths and making estimates on lengths.
Learn
This video looks at how to measure objects including making sure that the measurement tool is lined up to start at zero.
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question 1
What is the length of the line shown in the image?
Learn
When measuring an object we want to be as accurate as possible. With one end of the object at $0$0 on a ruler, the other end won't always line up with a whole number of inches or centimeters. Sometimes the nearest marking will be at a half-inch or fourth-inch instead.
For example, the blue line shown below has one end at $0$0 and the other end halfway between $2$2 and $3$3.
To measure this line, we can see that it is $2$2 full inches long, plus the extra half. So in total the line is $2\frac{1}{2}$212 inches long.
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question 2
What is the length of the line shown in the image?
Learn
This video shows us how we can estimate the length of an object, using items we know.
You might have noticed that meters and centimeters are spelled as 'meters' and 'centimeters' in the video. This is because that is the standard spelling in the metric system.
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question 3
Choose the best estimate for the length of your bed.
$6$6 inches
A$26$26 inches
B$76$76 inches
C
If an object doesn't line up with a whole number of units, we go to the nearest smaller whole value and then add the extra fraction.
When estimating length, $1$1 inch is roughly the distance from your fingertip to the first knuckle.