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Rounding to decimal places
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Foundational skills
Identify decimal place value
\[ \text{Example: } 24.63\underline{8} \rightarrow \text{Thousandths} \]
Identify which digit occupies a given decimal place value position.
Identify decision digit
\[ \text{Round } 5.273 \text{ to 1dp } \rightarrow \text{Look at } 7 \]
Identify the digit that determines whether a number rounds up or down.
Count decimal places
\[ 34.207 \rightarrow 3 \text{ decimal places} \]
Count the number of digits after the decimal point.
Rounding to nearest whole
Single-digit whole part
\[ 7.42 \rightarrow 7 \]
Round a decimal with a single-digit whole part to the nearest whole number.
Two-digit whole part
\[ 34.28 \rightarrow 34 \]
Round a decimal with a two-digit whole part to the nearest whole number.
Cascade
\[ 49.6 \rightarrow 50 \]
Round where the units digit is 9 and carries over.
Cascade to extra digit
\[ 99.7 \rightarrow 100 \]
Round where the result gains an additional digit.
Numbers less than 1
\[ 0.72 \rightarrow 1 \]
Round a decimal less than 1 to the nearest whole number.
Rounding to 1 dp
Simple rounding
\[ 3.472 \rightarrow 3.5 \]
Round to 1 decimal place.
Cascade from tenths
\[ 4.973 \rightarrow 5.0 \]
Round to 1 decimal place where tenths is 9 and carries over.
Two-digit whole part
\[ 23.468 \rightarrow 23.5 \]
Round a number with a two-digit whole part to 1 decimal place.
Cascade to extra whole digit
\[ 9.96 \rightarrow 10.0 \]
Round to 1 decimal place gaining an extra whole digit.
Numbers less than 1
\[ 0.472 \rightarrow 0.5 \]
Round a number less than 1 to 1 decimal place.
Trailing zero required
\[ 3.048 \rightarrow 3.0 \]
Round to 1 decimal place where the answer requires a trailing zero.
Rounding to 2 dp
Simple rounding
\[ 4.5231 \rightarrow 4.52 \]
Round to 2 decimal places.
Cascade from hundredths
\[ 5.297 \rightarrow 5.30 \]
Round to 2 decimal places where hundredths carries over.
Cascade through to whole
\[ 6.998 \rightarrow 7.00 \]
Round to 2 decimal places where carrying cascades to the whole number.
Numbers less than 1
\[ 0.4728 \rightarrow 0.47 \]
Round a number less than 1 to 2 decimal places.
Rounding to 3 dp
Simple rounding
\[ 2.45731 \rightarrow 2.457 \]
Round to 3 decimal places.
Cascade
\[ 4.53972 \rightarrow 4.540 \]
Round to 3 decimal places with cascading digits.
Trailing zeros required
\[ 5.12038 \rightarrow 5.120 \]
Round to 3 decimal places where the answer requires trailing zero(s).
Numbers less than 1
\[ 0.24816 \rightarrow 0.248 \]
Round a decimal less than 1 to 3 decimal places.
Special cases
Reverse rounding (1 dp)
\[ \text{Which round to 3.5? } 3.46, 3.42, 3.58 \]
Identify which numbers would round to a given 1 d.p. target.
Reverse rounding (2 dp)
\[ \text{Which round to 3.25? } 3.246, 3.254, 3.258 \]
Identify which numbers would round to a given 2 d.p. target.
Round to 1 and 2 d.p.
\[ 0.537 \rightarrow \text{a) } 0.5 \text{ b) } 0.54 \]
Round a 3 decimal place number to both 1 and 2 decimal places.
Timer (Optional)
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