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# Teaching Algorithms - PowerPoint PPT Presentation

Teaching Algorithms. How algorithms are taught Valerie Sereno. Simple Addition and Subtraction. Addition in Early Stage 1 and Stage 1 (K-2) are mostly taught horizontally: 3 + 4= 7 they do not move into vertical algorithms until late in year 2.

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## PowerPoint Slideshow about ' Teaching Algorithms' - kenna

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### Teaching Algorithms

How algorithms are taught

Valerie Sereno

• Addition in Early Stage 1 and Stage 1 (K-2) are mostly taught horizontally: 3 + 4= 7 they do not move into vertical algorithms until late in year 2.

• In early stage 1 (K) all are taught using diagrams or objects that the students can see and physically manipulate.

• Students need to know number facts i.e;knowing numbers before and after, counting backwards and forwards and skip counting.

• Students learn to use the bigger number and count on.

• Using doubles and near doubles; 7 + 8 = becomes 7 + 7 + 1= 15.

• Using combination s of 10 i.e 4 +6 and 7 +3 and bridging to 10 breaking down algorithms i. e 17+5, 17+3= 20 then 20+2=22 .

• Using related addition and subtraction factsie 8+7=15 and 15-7=8

• These cannot be applied unless the student has a thorough grasp of basic number facts.

• The process of trading in addition and subtraction has changed and is taught as a vertical algorithm.

• i. e T U T U

4 5 + 3 7 _

1 7 1 9

We no longer “borrow and pay back” we “trade”

H T U H T U

7 6 5 + 7 6 5 _

3 9 3 9

• Students MUST have a strong knowledge of number facts to understand and solve multiplication problems. Memorising the times tables means students can solve more difficult multiplication problems with much more ease.

• Multiplication does not get taught thoroughly until stage 2 (year 3)

• So 3 x 4 is basically 3+3+3+3 (or 4+4+4) (repeated addition)

• Mixed multiplication

T U T U

1 6 x 3 6 x

9 2 3

• To put it simply, it is “sharing”

• Division is taught more thoroughly again in stage 2.

• Is much easier if the student understands multiplication- as they can be seen as “related” 4 x 3 = 12 as 12 ÷ 4 = 3It can also be verbalised as how many times does 4 go into 12. Can also be seen as repeated subtraction.

• Division can be the most confusing of all processes but the best way for students who are struggling is to draw a diagram.

• It becomes difficult when dealing with “remainders” or “leftovers”- this is taught more thoroughly in stage 3 (yr 5-6)

r

• 4 68 4 67

r

12 144 12 149

As you can see these are solved due to knowledge of multiplication.

• Long Division can be taught but is no longer a mandatory part of the NSW mathematics curriculum in primary schools.