Solve equations involving the subtraction of two-digit numbers
I can solve equations involving the subtraction of two-digit numbers.
Solve equations involving the subtraction of two-digit numbers
I can solve equations involving the subtraction of two-digit numbers.
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Lesson details
Key learning points
- The known part can be partitioned into tens and ones before subtracting to help subtract two-digit numbers.
- Known facts and the partitioning of numbers can be used to help solve missing number equations.
Keywords
Partition - To split a whole up into parts - a piece or section of a whole.
Part - A piece or section of a whole.
Common misconception
Children may partition both the whole and the parts when subtracting two 2-digit numbers. They need to know to avoid this because it gives an incorrect answer when subtracting numbers which bridge 10
You may wish to explore further examples which do and do not reach the correct answer, articulating why this is the case and coming to the generalisation that, when subtracting, only one part needs to be partitioned into tens and ones.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Izzy wants to solve the equation 87 − 6 = ? Which is the most efficient strategy to use?
Q2.Andeep has £78 and he buys a unicorn. Which known fact should he use to calculate how much money he has left?
Q3.Match each equation to say which digit will change when it is solved.
The ones digit will change from 7 to 3
The tens digit will change from 7 to 3
Q4.Match the equations which will leave the same part remaining.
47 − 30 − 2 = ?
47 − 3 − 20 = ?
47 − 5 − 30 = ?
Q5.Fill in the missing number to solve the equation 76 − 35 = ?
Q6.Choose an equation to represent the number line.
Assessment exit quiz
6 Questions
Q1.Match the expressions which have the same value.
89 − 51
69 − 37
75 − 15
Q2.Which number is missing in the equation? 74 − 34 = 74 − − 4
Q3.Which equation is represented by the number line.
Q4.Find the missing part in the bar model.
