1. 8.24 rounded to 1 decimal place is 8.2
To round 8.24 to 1 decimal place…
... decide which two decimals it lies between ..
8.24
8.2
8.3
is nearer to 8.2.
8.24
because the 4 is less than 5 (half way) we round down
(the first decimal place is in blue (2) use the next digit to decide how to round)
8.24 rounded to 1 decimal place is 8.2

2. 4.1 4.2 4.15 4.15 4.15 rounded to 1 decimal place is 4.2
To round 4.15 to 1 decimal place…
... decide which two decimals it lies between ..
4.15
4.1
4.2
is half way.
If it’s half way we always round up.
4.15
because it’s 5 we round up.
4.15 rounded to 1 decimal place is 4.2

3. 7.63 16.79 7.63 rounded to 1 decimal place is 7.6
To round 7.63 to 1 decimal place
7.63
3 is less than 5 (half way) so round down
7.63 rounded to 1 decimal place is 7.6
To round to 1 decimal place
16.79
9 is greater than 5 (half way) so round up
16.79 rounded to 1 decimal place is 16.8

4. 2.781 0.816 2.781 rounded to 2 decimal places is 2.78
The 2nd decimal place is in blue – this is the number that changes
To round to 2 decimal places
2.781
1 is less than 5 (half way) so round down
2.781 rounded to 2 decimal places is 2.78
To round to 2 decimal place
0.816
6 is greater than 5 (half way) so round up
0.816 rounded to 2 decimal places is 0.82