Topic/Skill Definition/Tips
Topic: Accuracy Example
1. Place Value The value of where a digit is within a In 726, the value of the 2 is 20, as it is
number. in the ‘tens’ column.
2. Place Value The names of the columns that determine
Columns the value of each digit.
The ‘ones’ column is also known as the
‘units’ column.
3. Rounding To make a number simpler but keep its 74 rounded to the nearest ten is 70,
value close to what it was. because 74 is closer to 70 than 80.
If the digit to the right of the rounding 152,879 rounded to the nearest
digit is less than 5, round down. thousand is 153,000.
If the digit to the right of the rounding
digit is 5 or more, round up.
4. Decimal The position of a digit to the right of a In the number 0.372, the 7 is in the
Place decimal point. second decimal place.
0.372 rounded to two decimal places is
0.37, because the 2 tells us to round
down.
Careful with money - don’t write £27.4,
instead write £27.40
5. Significant The significant figures of a number are the In the number 0.00821, the first
Figure digits which carry meaning (ie. are significant figure is the 8.
significant) to the size of the number.
In the number 2.740, the 0 is not a
The first significant figure of a number significant figure.
cannot be zero.
0.00821 rounded to 2 significant figures
In a number with a decimal, trailing zeros is 0.0082.
are not significant.
19357 rounded to 3 significant figures
is 19400. We need to include the two
zeros at the end to keep the digits in the
same place value columns.
6. Truncation A method of approximating a decimal 3.14159265… can be truncated to
number by dropping all decimal places 3.1415 (note that if it had been
past a certain point without rounding. rounded, it would become 3.1416)
7. Error A range of values that a number could 0.6 has been rounded to 1 decimal
Interval have taken before being rounded or place.
truncated.
The error interval is:
An error interval is written using
inequalities, with a lower bound and an 0.55 ≤ x <0.65
upper bound.
The lower bound is 0.55
Note that the lower bound inequality can be The upper bound is 0.65
‘equal to’, but the upper bound cannot be
Mr A. Coleman Glyn School
Topic: Accuracy Example
1. Place Value The value of where a digit is within a In 726, the value of the 2 is 20, as it is
number. in the ‘tens’ column.
2. Place Value The names of the columns that determine
Columns the value of each digit.
The ‘ones’ column is also known as the
‘units’ column.
3. Rounding To make a number simpler but keep its 74 rounded to the nearest ten is 70,
value close to what it was. because 74 is closer to 70 than 80.
If the digit to the right of the rounding 152,879 rounded to the nearest
digit is less than 5, round down. thousand is 153,000.
If the digit to the right of the rounding
digit is 5 or more, round up.
4. Decimal The position of a digit to the right of a In the number 0.372, the 7 is in the
Place decimal point. second decimal place.
0.372 rounded to two decimal places is
0.37, because the 2 tells us to round
down.
Careful with money - don’t write £27.4,
instead write £27.40
5. Significant The significant figures of a number are the In the number 0.00821, the first
Figure digits which carry meaning (ie. are significant figure is the 8.
significant) to the size of the number.
In the number 2.740, the 0 is not a
The first significant figure of a number significant figure.
cannot be zero.
0.00821 rounded to 2 significant figures
In a number with a decimal, trailing zeros is 0.0082.
are not significant.
19357 rounded to 3 significant figures
is 19400. We need to include the two
zeros at the end to keep the digits in the
same place value columns.
6. Truncation A method of approximating a decimal 3.14159265… can be truncated to
number by dropping all decimal places 3.1415 (note that if it had been
past a certain point without rounding. rounded, it would become 3.1416)
7. Error A range of values that a number could 0.6 has been rounded to 1 decimal
Interval have taken before being rounded or place.
truncated.
The error interval is:
An error interval is written using
inequalities, with a lower bound and an 0.55 ≤ x <0.65
upper bound.
The lower bound is 0.55
Note that the lower bound inequality can be The upper bound is 0.65
‘equal to’, but the upper bound cannot be
Mr A. Coleman Glyn School
