Efficiently solve subtraction problems (within a whole) | Maths

Starter quiz

Look at this number $9 {{1} \over {4}}$ We say it as nine and one ______.

'quarter' ✓
Look at the part-part-whole model. What is the missing part?

2

7

${2} \over {7}$

${7} \over {2}$

8 ✓
$Which fraction shows how much of the bar has been shaded grey?$

Which fraction shows how much of the bar has been shaded grey?

${2} \over {4}$

${4} \over {2}$

${2} \over {6}$

${4} \over {6}$ ✓
Match the equations to their sum.

${1} \over {4}$ =

⇔

${3} \over {4}$ − ${2} \over {4}$ ✓

${2} \over {6}$ =

⇔

${5} \over {6}$ − ${3} \over {6}$ ✓

${6} \over {10}$ =

⇔

${9} \over {10}$ − ${3} \over {10}$ ✓

${1} \over {8}$ =

⇔

${3} \over {8}$ − ${2} \over {8}$ ✓
5 + ${2} \over {8}$ + $1{{3} \over {8}}$ + ${2} \over {8}$ = ?

${13} \over {8}$

$5{{8} \over {8}}$

$5{{5} \over {27}}$

$6{{7} \over {8}}$ ✓
$4{{3} \over {8}}$ + $2{{4} \over {8}}$ = ?

$6{{7} \over {16}}$

${13} \over {16}$

${13} \over {8}$

$6{{7} \over {8}}$ ✓

Exit quiz

Calculate: $1{{4} \over {5}}$ − ${2} \over {5}$ = ?

${2} \over {5}$

$1{{6} \over {10}}$

$1{{2} \over {5}}$ ✓

$1{{6} \over {5}}$
Match the equations to their difference.

$1{{3} \over {5}}$ =

⇔

$1{{4} \over {5}}$ − ${1} \over {5}$ ✓

$2{{2} \over {8}}$ =

⇔

$2{{6} \over {8}}$ − ${4} \over {8}$ ✓

$4{{4} \over {8}}$ =

⇔

$4{{7} \over {8}}$ − ${3} \over {8}$ ✓

$2{{1} \over {8}}$ =

⇔

$2{{4} \over {8}}$ − ${3} \over {8}$ ✓
$1{{5} \over {7}}$ − ___ = $1{{2} \over {7}}$

${7} \over {3}$

${1} \over {7}$

${3} \over {7}$ ✓

$2{{7} \over {7}}$
What is the missing number? $4{{5} \over {8}}$ − ______ = ${5} \over {8}$

'4' ✓
$5{{7} \over {10}}$ − $2{{4} \over {10}}$ = ?

$5{{3} \over {10}}$

${10} \over {3}$

$3{{3} \over {10}}$ ✓

$3{{10} \over {2}}$

$5{{3} \over {7}}$
Jacob has three and one-fifth metres of rope. Sofia has five and four-fifths metres of rope. How much more rope does Sofia have?

$2{{3} \over {10}}$

$2{{3} \over {5}}$ ✓

$2{{5} \over {3}}$

$8{{5} \over {5}}$

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Lesson Details

Key learning points

Mixed numbers can be partitioned in the same way as whole numbers.
If fractions have the same denominator, they can be subtracted.
To subtract fractions with the same denominator, the language of unitising can be used.

Common misconception

Children may subtract the incorrect parts of the mixed numbers and/or proper fractions.

What is the number that we are subtracting? If this number is a mixed number, partition it into its whole number part and fractional part.Use unitising to support subtraction.

Keywords

Mixed number - A mixed number is a whole number and a fraction combined. For example: one and a half is a mixed number.