CH2 Rounding

• Wiskunde
• Middelbare school
• havo, vwo
• Leerjaar 1

CH2 Rounding

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Write down:

1) Something you learned, 2) something you still want to ask.

1) Something you learned
2) Something you want to ask

Program:

• Start assignment (5 minutes)
• Homework check + quizizz (15 m)
• Instruction (15 m)
• Bettermarks (30m)
• Assignment page 2 (20m)

Today I'll learn... 

...how to round whole numbers

...how to round decimal numbers

...to identify situaties in which rounding is worthwile

Quizizz & homework check

Quizizz: https://quizizz.com/admin/quiz/66f0044c2c152b63455ef191?section=collections&searchLocale=

Instruction: Rounding

• When rounding, consider the digit to the ⁣right⁣ of the place you are rounding to.
• 0, 1, 2, 3, 4 --> you round down
• 5, 6, 7, 8, 9 --> you round up

• Rounding to the nearest thousands:
• 326 458⁣ ≈ ⁣326 000. ⁣

Round 908 to the nearest 10

1. 900
2. 910
3. 920
4. 901

Round 764 to the nearest 100

1. 700
2. 770
3. 704
4. 800

Round 614 to the nearest 10

1. 610
2. 620
3. 600
4. 630

Round 1486 to the nearest 1000

1. 1000
2. 1400
3. 1500
4. 2000

Round 235 to the nearest ten.

1. 200
2. 345
3. 240
4. 340

Rounding (2): upper & lower bound

• Given a rounded number, the range in which the original number can lie is given by an upper bound and a lower bound
• The equator is approximately ⁣40 100 km⁣ long. What length in kilometers could it actually be?
• 40 100⁣ has been rounded to the ⁣nearest hundred.
• So 40050 is the lower bound and 40149 is the upper bound, all numbers from ⁣40 050⁣ to ⁣40 149⁣ are possible.
• The length of the equator is between ⁣40 050 km⁣ (the lower bound) and ⁣40 149 km⁣ (the upper bound).

Rounding (3): decimal numbers

• The same rules apply for rounding decimal numbers as for ⁣natural⁣ numbers.
• Look at the place to the right of the one you need to round to.
• If the digit there is ⁣0, 1, 2, 3 or 4⁣ you round ⁣down. ⁣
• The digit in the place you want to round does not change. Rounding down makes the number ⁣smaller.
• If the digit there is ⁣5, 6, 7, 8 or 9⁣ you round ⁣up. ⁣
• The digit in the place you want to round increases by 1. Rounding up makes the number ⁣larger.

Round 23.07643 to thousandths

1. 23.08
2. 23.076
3. 23.07
4. 23.086

Round 23.07643 to tenths

1. 23.0
2. 23.1
3. 23.08
4. 23.07

Round 23.076496 to 5 decimal places

1. 23.07649
2. 23.07659
3. 23.07650
4. 23.07646

Round 31.00456987 to thousandths

1. 31.005
2. 31.004
3. 31.001
4. 31.002

Round 6.26427 to 2 decimal places.

1. 6.25
2. 6.26
3. 6.27
4. 6.3

Round 6.26427 to 1 decimal place.

1. 6
2. 6.2
3. 6.3
4. 6.5

Rounding (4): Everyday situations

• It is ⁣not⁣ always a good idea to use the rounding rules in real situations. Sometimes this can have a bad result.
• For example: repaper the walls of your room, 5.2 rolls becomes 6 instead of 5.

For example: you want to repaper the walls of your room, you calculate you need 5.2 rolls of wallpaper. In this case you havo to round up to 6 rolls of wallpaper, otherwise you wouldn't be able to finish you entire room.

Bettermarks

Make: 5.1, 5.2, 5.3, 5.6, 5.9

Done? Check your weekplanner.

Assignment decimal numbers

1. Check work of someone else 
2. Make page 2 

Evaluation

Homework: 

Make: 5.1, 5.2, 5.3, 5.6, 5.9

Today I'll learn... 

...how to round whole numbers

...how to round decimal numbers

...to identify situaties in which rounding is worthwile

For example: you want to repaper the walls of your room, you calculate you need 5.2 rolls of wallpaper. In this case you havo to round up to 6 rolls of wallpaper, otherwise you wouldn't be able to finish you entire room.