Rounding and approximation

Rounding and approximation

LEARNING GOAL: to understand how to round and use the leading digit to estimate values

RULE FOR ROUNDING

" 5 and above, give it a shove

4 and below, let it go"

​Rounding can be to a specified number of decimal places OR a place value.

​EXAMPLE 1

Round 8.58 to 1 decimal place / the nearest tenth.

8.58

​REMEMBER

"5 and above, give it a shove

4 or below, let it go"

​EXAMPLE 1

Round 8.58 to 1 decimal place / the nearest tenth.

8.68

​REMEMBER

"5 and above, give it a shove

4 or below, let it go"

​EXAMPLE 2

Round 5.1731 to 2 decimal places / the nearest hundreth.

5.1731

​REMEMBER

"5 and above, give it a shove

4 or below, let it go"

​EXAMPLE 2

Round 5.1731 to 2 decimal places / the nearest hundreth.

5.1731

​REMEMBER

"5 and above, give it a shove

4 or below, let it go"

Fill in the Blank

Round 6.934 to 1 decimal place

Fill in the Blank

Round 0.2512 to 1 decimal place

Fill in the Blank

Round 27.867 to 2 decimal places

Fill in the Blank

Round 9.123 to 2 decimal places

Fill in the Blank

Round 55.555 to the nearest whole number

Fill in the Blank

Round 6.934 to the nearest whole number

Fill in the Blank

Round 27.467 to the nearest ten

Fill in the Blank

Round 23,232.32 to the nearest thousand

​Repeating decimals

​Repeating decimals

​DOT or DASH?

​DOT or DASH?

Multiple Choice

convert to a decimal $$\frac{4}{5}$$  

• 0.6

• 0.8

• 1.0

• 0.3

Multiple Choice

convert to a decimal $$\frac{9}{11}$$  

• 0.12

• 0.8

• $$0.\overline{81}$$

• 0.888

Multiple Choice

convert to a decimal $$\frac{13}{6}$$  

• $$2.1\overline{6}$$

• 2.6

• 0.26

• 2.161616

Multiple Choice

convert the mixed number to a decimal:  $$1\frac{5}{6}$$  

• $$1.8\overline{3}$$

• 2.8888

• 1.838383

• 2.333

Multiple Choice

convert the mixed number to a decimal: $$12\frac{9}{10}$$  

• 12.8

• 12.9

• 12.1

• 12.3

Rounding and approximation

LEARNING GOAL: to understand how to round and use the leading digit to estimate values

LEADING DIGITS

Rounding to the leading digit can help us quickly approximate a value.

​Rounding

8 is the leading digit in the number 842

5 is the leading digit in the number 49.

​(The first number)

​In your head, can you quickly do the sum

692 + 57 + 1.2?

​In your head, can you quickly do the sum

692 + 57 + 1.2?

700 + 60 + 1.0?

Rounding to the leading digit means you can approximate quickly.

REMEMBER:

" 5 and above, give it a shove

4 and below, let it go"

Round each of the following numbers to the fi rst (or leading) digit.

1. 84 ≈ 

2. 120 ≈

3. 903 ≈

4. 5502

5. 23009 ≈

Multiple Choice

Round 78.25m to the nearest 10m

• 90

• 78

• 80

• 75

Multiple Choice

Round 38.23 to the nearest whole number

• 35

• 40

• 39

• 38

Multiple Choice

Round   $$\frac{80}{70}$$   to four decimal places

• 0.4658

• 1.1429

• 0.4822

• 0.4606

Multiple Choice

The estimated value of the product of 6.4 and 7.9 is

• 50.56

• 505.6

• 5.056

• 0.056

Multiple Choice

Round 348g to the nearest 10g

• 340g

• 345g

• 300g

• 350g

Multiple Choice

Use approximation to find 4 x 8.93

• 3.575

• 35.72

• 3572

• 0.3572

Multiple Choice

The approximate value of $$\frac{74.6}{3.8}$$ is

• 1.963

• 19.63

• 196.3

• 196.3

Multiple Choice

Which of the following numbers does NOT round to 400 when rounding to the nearest 100?

• 467

• 371

• 448

• 385

Multiple Choice

Eric bought 231 cows and Lisa bought 392 cows. Estimate how many cows they bought in total.

• 600 cows

• 1,000 cows

• 700 cows

• 500 cows

Multiple Choice

Round $1 238.51 to the nearest dollar.

• $1 000

• $1 200

• $1 240

• $1 239