Written Methods for Multiplication in KS2 Firfield Primary School Wednesday 25 th November 2015

KS1 – Y3 Mainly single digits x single digit Repeated Addition (4 x 6) = Children use a number line or beads to support their understanding Use of inverse facts to complete number sentences (? X 5 = 20)(3 x ? = 18) (? X ? = 32) Lots of times table practise and division facts linked with them. Which leads us on to partitioning…

Hang on, what’s partitioning? For bigger numbers (TU x U) we partition the number into separate TENS and UNITS: 38 x 5 = (30 x 5) + (8 x 5) = (150)+ (40) = x 5 = 30 x 5 = 150 (3 x 5 = 15 so 30 x 5 = 150) 8 x 5 =

Grid Method (TU x U) A more formal way to set things out Makes links to x by a multiple of x 7 = (30 x7) + (8 x7) = = 266 Estimate first (approx. 40 x 7 = 4 x 7 x 10) X

Grid Method (TU x TU) Same as previous method Now with extra boxes! 72 x 38 (approx. 70 X 40 = 2800) Use column addition method to total = 2736 x

Short Multiplication (x U) The one the adults in the room recognise! Initially emphasise the place value and partitioning skills from previous methods. Multiply UNITS first then TENS… 3 8 X

Short Multiplication (X TU) Expanded to Multiply by Tens and Units Remember the zero (when x10) X 1 6 x

Remember Children will be taught a range of calculation methods (mental and written). Children will choose different methods depending on the task. Children will not move on to the next stage if: They are not ready They are not confident Once children are using concise methods they will not go back to expanded methods. Children should be encouraged to estimate answers Children should be encouraged to check their answers using inverse operations or simple re-calculating. Children should consider when mental calculations are more appropriate

How you can help Regular practise of times tables Know square numbers, doubles, x 10 Explaining how to multiply any number by 10, 100 or 1,000 by showing how digits move to the left. By showing the links between x table facts such as: 5 x 6 = 30 so 5 x 60 = 300 or 50 x 60 = 3,000 By showing partitioning and explaining place value Regular practise of written methods now that you understand how to use them! (use it or lose it) Regular mental calculations that rely on partitioning and an understanding of place value (what’s 42 x 5?) (40 x x 5 = 4 x 5 =20 so 40 x 5 = x 5 = 210)