9 Rounding decimals mostly Level 2

Mostly Level 2
ROUNDING DECIMALS
What you need to be able to do:
Level 1 – round to 2 decimal places
Level 2 – Rounding up to 4 decimal places.
Click here and look in Sections 1, 2 and 3 for rounding activities.
Come back to this activity if you are still not sure.
Decimal places are the numbers after the decimal point
2.3
has 1 decimal place
2.35
has 2 decimal places
2.358
has 3 decimal places
2.3589 has 4 decimal places
A
How many decimal places do these numbers have?
1)
3.1
2)
7.98
3)
2.5
4)
9.087
5)
76.35
6)
670.2
7)
4.0001
8)
0.8
9)
3.999
10) 763.5
Sometimes, when you have a lot of decimal numbers you have to
ROUND OFF
0
1
2
3
4
5
f l ex i p
4 or below
KEEP THE SAME
ac k s
6
7
5 or above
ROUND UP
1
8
9
Mostly Level 2
Rounding Money - For money we need 2 decimal places – so look at
the third place.
£1.759 the third place is a 9 - so round up to £1.76
£1.752 the third place is a 2 - so keep it at £1.75
£11.574 the third place is a 4 - so keep it at £11.57
£11.575 the number after the pence is a 5 - so round up to £11.58
B
Have a go at these yourself:
1)
£1.347
the number after the pence is a 7 - so round up to______
2)
£1.463
the number after the pence is a 3 - so keep it at_______
3)
£36.501 keep it at
_______
4)
£78.185 round up to
_______
5)
£3.988
6)
£4.674
Now you have had some practise at rounding, so we can start
to use it with any decimal number.
If you are rounding off to 2 decimal places it is just the same as
when you were rounding off money.
f l ex i p
Look at these …..
£5.177 rounds off to £5.18
5.177 rounds off to 5.18
£37.192 rounds to £37.19
37.192 rounds to 37.19
ac k s
2
Mostly Level 2
Every time you round off to two decimal places you
LOOK AT THE NEXT DECIMAL NUMBER ALONG (the 3rd number).
If it’s 5 or above, round up
If it’s four or below, keep the number the same (round down)
Have a look at these examples. Then have a go at the questions.
C
3.755
round up to
3.76
9.521
round down to
9.52
9.52189
still round down to 9.52
1)
0.97222
2)
27.471
3)
0.123
4)
27.479
5)
3.088112
6)
3.0069
7)
6.18915
8)
4.0049
9)
3.175
10) 10.991
You do the same thing when you round to 1 decimal place
Every time you round off to 1 decimal place you
LOOK AT THE NEXT DECIMAL NUMBER ALONG (the 2nd number).
If it’s 5 or above, round up
f l ex i p
If it’s four or below, keep the number the same (round down)
5.73
round down to
5.7
7.35
round up to
7.4
6.18375
round up to
6.2
ac k s
3
Mostly Level 2
D
Round these to one decimal place
1)
5.92
2)
11.572
3)
11.549
4)
107.251
5)
21.33
6)
37.517
7)
0.55
Sometimes there is another step when rounding off.
Look at these examples:
£1.699 rounded of to 2 decimal places is £1.70
0.395 rounded of to 2 decimal places is 0.40
5.297 rounded of to 2 decimal places is 5.30
Can you see what is happening?
Include this last 0,
because it asks for 2
decimal places
We are rounding up but because the number we are rounding up is
a 9, it has a knock on effect (like if you add 1p to £1.59)
E
Try these examples yourself:
1)
£1.698 to 2 decimal places
2)
£8.296 to 2 decimal places (2d p)
3)
12.595
to 2 d p
4)
0.099
to 2 d p
5)
£1.999 to 2 d p
6)
0.999
to 2 d p
7)
1.97
to 1 decimal place
8)
34.98
to 1 decimal place (1 d p )
9)
0.99
to 1 d p
10) 9.95
to 1 d p
You may need to round off when you divide decimals (see ‘Dividing
Decimals by Whole Numbers’).
f l ex i p
Sometimes you might get a recurring number …. where the sum goes
on and on. When this happens you need to round off like this.
ac k s
4
Mostly Level 2
0.7
3 ) 2.22
0.733
3 ) 2.210101
This will carry on forever.
We need to round it off (usually to 2
decimal places) so 0.73333 = 0.73
0.7333
3 ) 2.21010101
F
Try dividing these with a calculator. Round to 2 decimal places.
1)
£2.75
3
2)
£40.00
6
3)
22.00
7
4)
7.5
9
5)
1.0
3
Lastly, round each of these numbers off to 1, 2 and 3 decimal
places ………
2.3456
6)
3.1749
1 decimal place
2.3
2 d p
2.35
3 d p
2.346
1dp
2dp
3dp
7)
41.0733
1
2
f l ex i p
3
ac k s
5
Mostly Level 2
Answers
Decimal Places And Rounding Off
How many decimal places?
1
2
1
3
2
1
4
1
3
1
B
1)
2)
3)
4)
5)
6)
Rounding Money
£1.35
£1.46
£36.50
£78.19
£3.99
£4.67
C
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
Rounding to 2 decimal places
0.97
27.47
0.12
27.48
3.09
3.01
6.19
4.00
3.18
10.99
f l ex i p
A
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
ac k s
6
D
1)
2)
3)
4)
5)
6)
7)
Rounding to 1 decimal place
5.9
11.6
11.5
107.3
21.3
37.5
0.6
E
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
£1.70
£8.30
12.60
0.10
£2.00
1.00
2.0
35.0
1.0
10.0
F
1)
2)
3)
4)
5)
6)
7)
0.91666
6.66666
3.14285
0.83333
0.33333
3.2
3.17
3.175
41.1
41.07
41.073
rounds off to
rounds off to
rounds off to
rounds off to
rounds off to
0.92
6.67
3.14
0.83
0.33

Download Report