addition and subtraction on a number line links between the model and appropriate ‘vertical’...

Addition and subtraction on a number line links between the model and

appropriate ‘vertical’ method

Janine Blinko

421-273

421-273

421

-200

221

In which case they need to be fluent in subtracting multiples of 100 from any number……

Equivalent written recording-formal version

421-273221 -200

421-273

and fluent in subtracting multiples of 10 from any number including crossing the hundreds boundaries……

Equivalent written recording-formal version

421-273221 -200151 -70

421

-200

221

-70

151

421-273

-3

148 421

-200

221

-70

151

Equivalent written recording-formal version

421-273221 -200222 -70148 -3

91-68

+2

68 91

+1

23

+20

70 90

It is 11.25. My cake will be ready at 1.15. How long do I have to wait before it is ready?

+5 mins

11.25 1.15

+1 hour

1hour 55 minutes

+30 mins

11.30

+15 mins

1.0012.00

421-273

+7

273 421

+100

148

+20

280

+21

400300

Equivalent written recording-formal version

421-273 7 280 20 300100 400 21 421148

421-273

-3

148421

-200

221

-70

151

Equivalent written recording-formal version

421-273221 -200222 -70148 -3

421-273

-3

148 421

-200

221

-70

151

Equivalent written recording-formal version

421-273221 -200222 -70148 -3

148+273

148+273

148

+200

348

In which case they need to be fluent in adding multiples of 100 to any number……

Equivalent written recording-formal version

148+273348 +200

148+273

148

+200

348

and fluent in adding multiples of 10 to any number including crossing the hundreds boundaries……

+70

418

Equivalent written recording-formal version

148+273348 +200418 +70

148+273

148

+200

348

+70

418

+3

421

Equivalent written recording-formal version

148+273348 (+200)418 (+70)421 (+3)