Jonas making number bonds for 32.Anchor Green Primary School,SingaporeThe lesson began with this task – which number isbigger? Bigger by how much? This is to helpstudents link subtraction with comparison situation.
A few observations made by observers.• The students were excited.• The students were usually not told if their answer is right or wrong.• The teacher got many students to publicly share their answer.• The students had to do mental math.Some questions:• How often does the students get to learn tricks like this?• Did the students asked how the trick works?Did you observe the focus on thinking and problemsolving as well as a focus on conceptualunderstanding of subtraction and the skill ofsubtraction with renaming?
32 = 20 + 10 + 2 Subtract 4 from 10 Two strategies were evident. One of them involves 10 – 4 + 2 . 32 = 20 + 12 Subtract 4 from 12Anchor Green Primary School, SingaporeReview of Subtraction Procedure6 minutes
There were also a few situations that wediscouraged teachers from doing – did you pickedthose up? Students were given 1, 2, 5 and 8 and asked to make numbers and subtracting the smaller number from the larger.