Rounding Numbers.

6 7 8

6.3 7.2 7.8

2035 = 2040

8985 = 90006.89 = 6.9

67 890 = 68 000

Rounded Numbers All Around You.

Here are some examples of rounded numbers which could appear in newspaper headlines:

30 000 Watch Scotland Win Again.

Man Leaves £2 Million To Charity.

500 000 March In War Protest.

©Microsoft Word clipart

Rounding To The Nearest Whole Number.

Consider the number :

6.7

It is our task to decide if the number is closer to :

6 or 7 Look at the number line below:

6 7 8

Mark the number 6.5

6.5

Mark the number 6.7

6.7

Is 6.7 closer to 6 or 7 ?

6.7 = 7 (to the nearest whole number)

6.5 is the midpoint between 6 and 7.

Is 6.7 above or below 6.5 ? Above

Further Example.Round the following to the nearest whole number:

(1) 24.3

24 25 26

What is the midpoint between 24 and 25 ?

24.5

Is 24.3 above or below 24.5 ?

24.3

Below.

24.3 = 24 (To the nearest whole number).

What Goes In The Box ?Round the following to the nearest whole number:

(1) 4.8

(2) 7.4

NB: always round 0.5 up . Ie 12.5 = 13 (to the nearest whole number).

(3) 44.6

(4) 87.5

(5) 56.3

(6) 287.6

(7) 9.8

(8) 49.6

(9) 99.7

(10) 399.5

5

7

44

88

56

288

10

50

100

400

Rounding To 1 Decimal Place.

Round 4.67 to one decimal place (1d.p).

4.6 4.7

Mark 4.67 on the number line .

4.67

Is 4.67 closer to 4.6 or 4.7 ? 4.7

4.67 = 4.7 (to 1d.p)

What number is the arrow pointing at ?

4.65

4.65

Round 19.53 to 1 d.p .

19.5 19.6

Mark 19.53 on the number line .

19.53

Is 19.53 closer to 19.5 or 19.6 ? 19.5

19.53 = 19.5 (to 1d.p)

What number is the arrow pointing at ?

19.55

19.55

What Goes In The Box ? 2Round the following to 1 decimal place.

(1) 34.67 =

(2) 17.72 =

(3) 24.75 =

(4) 41.92 =

(5) 56.95 =

(6) 39.97 =

(7) 99.96 =

(8) 999.95 =

34.7

17.7

24.8

41.9

60

40

100

1000

Rounding To 2 Decimal Places.In order to make this a faster process we will take a different approach:

Round 45.678 to 2 decimal places ( 2 d.p).

What number is the second after the point ? 7

Is the number after the seven greater or smaller than 5 ?

8 is greater than 5 (or 8 > 5) Rule

If the number is greater than or equal to 5 then round up.

Now round 45.678 to 2 d.p

45.678 = 45.68 (to 2 d.p)

Round 23.482 to 2 decimal places ( 2 d.p).

What number is the second after the point ? 8

Is the number after the eight greater or smaller than 5 ?

2 is less than 5 (or 2 < 5) Rule

If the number is greater than or equal to 5 then round up.

Now round 23.482 to 2 d.p

23.482 = 23.48 (to 2 d.p)

What Goes In The Box ? 3

Round the numbers below to 2 decimal places.

(1) 45.783 =

(2) 37.677 =

(3) 6.4589 =

(4) 0.4291 =

(5) 36.995 =

(6) 99.992 =

(7) 0.097 =

(8) 999.9958 =

45.78

37.68

6.46

0.43

37

99.99

0.1

1000

Rounding To The Nearest 10,100,1000 etc.

Round 467 to the nearest ten.

Which number is the tens number ? 6

Is the number after the 6 greater or smaller than 5 ? 7 > 5

Rule

If the number is greater than or equal to 5 then round up.

Now round 467 to the nearest ten.

467= 470 (to the nearest ten).

460 470467

Round 23 438 to the nearest hundred.

Which number is the hundreds number ? 4

Is the number after the 4 greater or smaller than 5 ? 3 < 5

Rule

If the number is greater than or equal to 5 then round up.

Now round 23 438 to the nearest hundred.

23 438= 23 400 (to the nearest hundred).

23 400 23 50023 438

What Goes In The Box ? 4

Round the numbers below to the required unit:

(1) 34 567 to the nearest ten =

(2) 47 943 to the nearest hundred =

(3) 356 518 to the nearest thousand =

(4) 356 218 to the nearest ten thousand =

34 570

47 900

357 000

360 000