Primary School Decomposition DECOMPOSITION A

…. . Primary School Decomposition

DECOMPOSITION A definition The breakdown of numbers into component parts.

What do the children need to know before beginning decomposition. n. A pre-requisite to your child learning about decomposition is a secure knowledge of place value ( tens and units). The acquisition of this knowledge will determine when decomposition is introduced to your child.

In our school place value is introduced in Primary 3 using a range of different strategies Ø Practically using a variety of apparatus. Ø Mentally Ø Pencil and paper methods.

Decomposition – an example n 14 – 7=? SPEAK THE SUM n Fourteen take away seven equals ? n Fourteen subtract seven equals? n Fourteen minus seven equals? n Find the difference between fourteen and seven.

The children can approach this sum in a variety of ways Ø Ø Ø Use the number line to count back 7 from 14. Use their knowledge of addition in reverse of subtraction e. g. (7 + 7 = 14) therefore (14 – 7 = 7) By rounding and adjusting e. g. 14 – 7 = is the same as 14 – 10 + 3 = 7 By counting on 47 – 25 (+ 5 (30)+ 10(40) +7(47) By partitioning 47 – 25 is the same as 47 – 20 – 5

Pencil and paper method n When the numbers that the children are working with become larger, they need to then learn the strategy of using the pencil and paper method of calculation. 94 – 47 = ? The school has two main methods of approaching this calculation.

The language used at this stage is very important. 94 - 47= ? Method 1 n n n n Four take away seven. Go to tens side. Take one ten over to units side. Exchange the ten for ten units/ones. Add on the four – make 14 14 take away seven Leaves seven. Eight tens left. 94 -47 47

Method 2 n n n n n Seven from four (cannot take). Go to tens house. Take one ten over to the units house. Exchange the ten for ten units. Add on to the four – makes 14. Take seven away from 14. Leaves seven. Move to tens house Eight tens left. 94 - 47 47

IT IS THE POLICY OF THE SCHOOL, NOT TO USE THE TERMS ‘BORROW’ OR ‘PAY’ BACK.

How can I help my child with decomposition. Try not to become frustrated/angry if your child does not gain an understanding of these complex calculations straight away. n Encourage your child to think of larger numbers being made up of a combination of smaller numbers e. g. 356 is the same as 300 + 50 + 6 n

n Encourage your child to think of subtraction/decomposition as the inverse of addition e. g. 7 + 3 = 10 3 + 7 = 10 10 – 7 = 3 10 – 3 = 7 q Help your child to think in tens Forty four (44) 40 and four Four tens and four units/ones.

Finally decomposition is a big milestone in Primary Education. Some children may find it very difficult to begin but with plenty of practice and support both in school and at home they should achieve success.

As always, if your child is having problems with decomposition at home please do not hesitate to contact the school.