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- NZ Year 4 Maths
- Introduction to Decimals

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Get Started Now- Intro Lesson: a8:16
- Intro Lesson: b12:28
- Lesson: 1a1:30
- Lesson: 1b1:59
- Lesson: 1c2:29
- Lesson: 1d2:17
- Lesson: 2a2:58
- Lesson: 2b2:59
- Lesson: 2c2:48
- Lesson: 2d2:40
- Lesson: 3a4:02
- Lesson: 3b3:40
- Lesson: 3c5:15
- Lesson: 4a3:01
- Lesson: 4b3:30
- Lesson: 4c4:07
- Lesson: 4d6:39

In this lesson, we will learn:

- How to use number lines to help estimate decimal values (to the closest whole number or closest tenth)
- How to round decimal numbers to the nearest whole number, or the nearest tenth

- To
means to roughly guess the value (or a rough calculation)__estimate__ - For
**estimating decimals**, have less decimal place values in your number is one strategy for estimation; by making numbers less exact (less precise), they become simpler or easier to do math with__Rounding__- We use the
**symbol**$\approx$ meaning "about equal to" for estimation and rounding - Ex. 39 is about equal to the even number 40; 39 $\approx$ 40
- We can use
**number lines**to help estimate decimal values - Find the closest distance to the
__nearest whole number__OR the__nearest tenth__ - Ex. rounding 0.3 to the nearest whole number, is it closer to 0 or 1?

- 0.3 is closer to 0 than it is to 1. Therefore, 0.3 $\approx$ 0

- Ex. rounding 0.66 to the nearest tenth, is it closer to 0.6 or 0.7?

- 0.66 is closer to 7 than it is to 6. Therefore, 0.66 $\approx$ 0.7

- The steps for rounding numbers:
- Look at the place value you are rounding to ("
**target**").

$\quad \, \longrightarrow \;$ start writing a new rounded number, where:

$\quad \, \longrightarrow \;$ any smaller place values (to the right) can be changed to zero

$\quad \, \longrightarrow \;$ any bigger place values (to the left) can be kept - Look at the place value to the right of where you are rounding to.
- if the digit is $\geq 5$, round up (increase the
**target**by 1) - if the digit is < 5, round down (keep the
**target**the same)

- if the digit is $\geq 5$, round up (increase the
- Any trailing zeroes in decimals can be removed (i.e. 0.50 = 0.5; 2.0 = 2)

- When your
**target digit**is 9, if you round up then you will**regroup**to the next place value up. - Ex. Rounding 0.97 to nearest tenth $\, \longrightarrow \,$ round up from 0.9 to 1.0; 0.97 $\approx$ 1.0

- IntroductionIntroduction to Estimating Decimals:a)How to estimate decimal values using number linesb)How to round decimal numbers
- 1.
**Using number lines to round decimals**

Use the number line to help you round the decimal. Draw an arrow pointing to:a)the nearest whole number

b)the nearest tenth

c)the nearest whole number

d)the nearest tenth

- 2.
**Rounding decimals to different place values**

Round the decimal to the specified place value.a)Round 51.4 to the nearest whole number.b)Round 36.78 to the nearest tenthc)Round 6.29 to the nearest whole number.d)Round 2.95 to the nearest tenth. - 3.
**Comparing relative decimal values**

Compare the relative decimal and fraction values to answer.a)Write whether each decimal is more than, less than, or equal to $\large \frac{1}{2}$- 0.49
- 0.50
- 0.68

b)Determine if these decimals are more than, less than, or equal to $\large \frac{1}{4}$- 0.4
- 0.16
- 0.25

c)A strawberry jam recipe needs 2$\large \frac{3}{4}$ pounds of strawberries. Margot weighs three different boxes at the store. Which box should she buy so that she has enough for the recipe? Why? - 4.
**Estimating decimal values from picture representations**

Estimate the decimal value represented by the picture. Answer using the $\approx$symbol.

Hint: Try to create equal divisions.a)b)c)d)