Session W8 Yeap Ban HarWhole Numbers www.banhar.blogspot.comMultiplication & Division

Learning & Reviewing Basic Facts

Some ways to help students acquire and consolidate basic facts.

2 x 4 = 83 x 4 = 8 + 4

2 x 4 = 84 x 4 = 8 + 8

2 x 4 = 85 x 4 = 207 x 8 = 8 + 20

10 x 4 = 40 9 x 4 = 40 – 4

Da Qiao Primary School, Singapore

The product is 48.

She has 6. What

do I have?

Multiplication & Division of Large

Numbers

Some ways to help students make sense of computation algorithm

Find the value of 34 x 2 .

3 4 x 26 0+ 86 8

3 4 x 20 86 06 8

Find the value of 34 x 3 . 3 4

x 39 01 2

3 4 x 31 29 0

The concrete and the visuals help develop meaning i.e. multiplying the tens and ones separately.

3 4 x 39 01 2

The expanded notation emphasizes 34 as 3 tens and 4 ones which are then dealt with separately.

Quantities with different ‘nouns’ are dealt with separately.

Find the value of 28 x 32 .

To see 28 as 20 and 8 and 32 as 30 and 2.

This leads to the idea of (a + b)(c + d).

xUse the digits 0 to 9 no more than once to make a correct multiplication sentence.

The class had four solutions32 x 15 = 48012 x 65 = 78012 x 48 = 57639 x 12 = 468

12 x 43 did not work.

12 can be seen as 10 and 2.Thus, 12 x 65 can also be computed as the sum of 10 x 65 and 2 x 65 i.e. 650 + 130.

12 can be seen as 10 and 2.Thus, 39 x 12 can also be computed as the sum of 39 x 10 and 39 x 2 i.e. 390 + 78.

Alternatively, 40 x 12 can be used to compute 39 x 12.

The use of number bonds to compute large numbers gives students opportunities to develop their number sense.

Find the value of 7081 3 .

Using number bonds, 7081 is 6000, 900, 180 and 1. Each is then divided by three.