Transcript Rounding Numbers

Rounding Numbers.
6
8
7
6.3
2035 = 2040
7.2
7.8
67 890 = 68 000
8985 = 9000
6.89 = 6.9
Rounded Numbers All Around You.
Here are some examples of rounded numbers
which could appear in newspaper headlines:
30 000 Watch Scotland Win Again.
500 000 March In War Protest.
Man Leaves £2 Million To Charity.
Rounding To The Nearest Whole Number.
6.7
Consider the number :
It is our task to decide if the number is closer to :
6
or
Look at the number line below:
7
6
6.5 6.7
Mark the number 6.5
7
8
6.5 is the midpoint between 6 and 7.
Mark the number 6.7
Is 6.7 closer to 6 or 7 ?
Is 6.7 above or below 6.5 ?
6.7 = 7 (to the nearest whole number)
Above
Further Example.
Round the following to the nearest whole number:
(1) 24.3
24 24.3 24.5
25
What is the midpoint between 24 and 25 ?
Is 24.3 above or below 24.5 ?
Below.
24.3 = 24 (To the nearest whole number).
26
What Goes In The Box ?
Round the following to the nearest whole number:
NB: always round 0.5 up . Ie 12.5 = 13 (to the nearest whole number).
(1) 4.8
5
(6) 287.6
288
(2) 7.4
7
(7) 9.8
10
(3) 44.6
44
(8) 49.6
50
(4) 87.5
88
(9) 99.7
100
(5) 56.3
56
(10) 399.5
400
Rounding To 1 Decimal Place.
Round 4.67 to one decimal place (1d.p).
4.6
4.7
4.65
4.67
What number is the arrow pointing at ?
Mark 4.67 on the number line .
Is 4.67 closer to 4.6 or 4.7 ?
4.67 = 4.7 (to 1d.p)
4.7
4.65
Round 19.53 to 1 d.p .
19.5
19.6
19.53
19.55
What number is the arrow pointing at ?
19.55
Mark 19.53 on the number line .
Is 19.53 closer to 19.5 or 19.6 ?
19.53 = 19.5 (to 1d.p)
19.5
What Goes In The Box ? 2
Round the following to 1 decimal place.
(1) 34.67 =
34.7
(5) 56.95 =
60
(2) 17.72 =
17.7
(6) 39.97 =
40
(3) 24.75 =
24.8
(7) 99.96 =
100
(4) 41.92 =
41.9
(8) 999.95 = 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
Now round 45.678 to 2 d.p
If the number is
greater than or equal
to 5 then round up.
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
Now round 23.482 to 2 d.p
If the number is
greater than or equal
to 5 then round up.
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 = 45.78
(5) 36.995 =
37
(2) 37.677 = 37.68
(6) 99.992 =
99.99
(3) 6.4589 = 6.46
(7) 0.097 =
0.1
(4) 0.4291 = 0.43
(8) 999.9958 = 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
Now round 467 to the nearest ten.
467= 470 (to the nearest ten).
460
467
If the number is
greater than or equal
to 5 then round up.
470
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
Now round 23 438 to the nearest hundred.
23 438= 23 400 (to the nearest hundred).
Rule
If the number is
greater than or equal
to 5 then round up.
23 400
23 438
23 500
What Goes In The Box ? 4
Round the numbers below to the required unit:
(1) 34 567 to the nearest ten =
34 570
(2) 47 943 to the nearest hundred =
47 900
(3) 356 518 to the nearest thousand =
357 000
(4) 356 218 to the nearest ten thousand =
360 000