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### Course: 3rd grade foundations (Eureka Math/EngageNY) >Unit 2

Lesson 1: Topic A: Foundations

# Measuring lengths with different units

Use different units to measure the same object.

## Measuring lengths with different units

Let's measure a fence with squirrels!
The fence is $10$ squirrels long.
Now let's measure the same fence with ponies.
The fence is $5$ ponies long.
Why did it take fewer ponies to measure the length of the fence?

### Practice problem 1

This is a rectangle.
Let's measure the $\text{blue line}$ below using both rectangles and a centimeter ruler:
The line is
rectangles long.

The line is
centimeters long.

The width of each rectangle is _____ than a centimeter.

So, it takes _____ rectangles than centimeters to measure the line.

### Practice problem 2

Measure the $\text{green line}$ using the centimeter ruler.
The line is
centimeters long.

Now, measure the $\text{green line}$ using the inch ruler.
The line is
inches long.

It takes _____ centimeters than inches to measure the line.

So, a centimeter is _____ than an inch.

### Challenge question

Raj measures the height of a desk with his pencil. He finds out the desk is $8$ pencils tall. Lynn measures the same desk with her pen. The desk is $9$ pens high.
Which is longer?

## Want to join the conversation?

• On practice problem one, why did it ask about the width of the rectangle when it should've asked the length. Clearly the width was the same as a centimeter, and the length was shorter. When I answered shorter it said correct.
• The width is on the bottom, the length is on the side, that is why it is width
• How many inches was Raj's pencil?
(1 vote)
• The whole thing here is that we don't know. If Raj had a larger pencil, the desk would be less than 8 pencils tall. If Raj sharpened his pencil a bit, the desk would be more than 8 pencils tall. We can't know exactly how tall Raj's pencil was in our normal units without knowing the height of something else in normal units, like the pen or the desk. In terms of the pen's length, Raj's pencil is 9/8 of the pen.
• It asks how high a desk is and Raj is 8 pencils long and Lynn is 9 and it says Raj is longer?
• Since Raj measures the height of a desk with his pencil, and finds out the desk is 8 pencils tall, then Lynn measures the SAME desk with her pen, and finds it is 9 pens high, Lynn's pen must be shorter than Raj's pencil. Therefore, Raj's pencil is longer than Lynn's pen.
• what are units?
• Units are specific sections or amounts of things (such as time, length, volume, etc.) that we use for measurement. Some examples of units are seconds, centimetres, and millilitres.
• Why is cm. shorter then in.? Who invented it?
• because cm = 1/100 of m and an inch is equal to 1/12 of a foot and one meter is about one yard and one yard is 3ft
• how is that a challenge?
(1 vote)
• For the last question if Lynn's desk was 9 pens long then why was Raj's desk longer?
• They're measuring the same desk with different materials. Therefore, since Raj's pencil took only 8, it means that the pencil was longer.