Addition and subtraction Flashcards
What are the key words of a sum?
34 + 56 = 90
Addend + Addend = Sum/Total
What are the key words of a sum?
45 - 13 = 32
Minuend - Subtrahend = Difference
What are the two important categories in addition?
- Union of two sets - Think about the language – ‘How many altogether?’
- Counting on and increasing
- Union of two sets - Think about the language – ‘How many altogether?’
- Counting on and increasing
Examples?
In pairs discuss the word stories you could make up for 13 + 4 for each category above:
e.g. 13 blue counters and 4 red counters – How many counters are there altogether?
I am on square 13 in snakes and ladders and I throw a 4 on the dice – What square am I on now?
What is the name of a structure which involves the union of two sets?
Aggregation structure (combining) so for instance a circle with 4 counters another with 3 counters and then the total 7.
What is the counting on and increasing structure called?
Augmentation structure (Number line) like counting on.
What is compensating on a number line?
Is when we take away something on a number line.
What is the Commutative Law?
a + b = b + a (4 + 5 = 5 + 4)
We cannot use this law for subtraction as it leads to misconceptions, e.g. 9 – 5 = 5 – 9?
What is the Associative Law?
a + ( b + c) = (a + b) + c
12 + (6 + 2) = (12 + 6) + 2
What are the five key structures of the subtractions?
- Partitioning – e.g. ‘How many are left?’
- Comparison – e.g. ‘How many more/less?’
- Complement of a set
- Reduction – counting back
- Inverse of addition
What are the partitioning structures?
Take away
How many are left?
https://canvas.wlv.ac.uk/courses/28907/pages/session-4-addition-and-subtraction-1
What’s the comparison structure?
‘difference’
Fill the gap… How much older? How much heavier?
(Numberlines?)
What is complementary addition?
How many more to make?’
I have 37p but I want to buy some chocolate that is 49p. How much more do I need?
What is The Reduction Structure?
Counting back
The chocolate bar was 12p. The shop thought it was too expensive and took 3p off.
Count back (from the correct number), reduce.
- Addition as the Inverse of Subtraction
Key words – undoing and reversing
a - b = c then c + b = a
10 - 7 = 3 then 3 + 7 = 10
What are the key terms of subtraction and addition
In addition it’s called the total or the sum
In subtraction its called the difference
Negative numbers
Partitioning both numbers you add them to get the number together.
If subtraction you are only partitioning one number
