Lesson · Grade 2 · Mathematics
Subtracting on an open number line
- Grade 2
- Mathematics
- 58 s
- British Columbia
- BC2-MA-11
A frog starts at 64 on an open number line and works out 64 − 23 by jumping back by tens to 54 and 44, then hopping back by ones to 43, 42 and 41, while 2 rods of ten and 3 single cubes fade as each jump uses them. It lands on 41, fills in 64 − 23 = 41, checks it with 41 + 23 = 64, and ends on the recap "Jump back by tens, then by ones."
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In one sentence
The question this lesson answers
What is 64 take away 23?
An open number line shows only the numbers we need.
Transcript
What the lesson says
What is 64 take away 23?
An open number line shows only the numbers we need.
Our frog starts at 64, near the right end.
23 is made of 2 tens and 3 ones.
First, jump back by tens, one ten at a time.
64 take away 10 is 54.
54 take away 10 is 44.
Now hop back by ones, three small hops.
Hop, 43. Hop, 42. Hop, 41.
The frog has landed on 41.
So 64 take away 23 is 41.
Let's check: 41 plus 23 is 64.
Jump back by tens, then by ones.
Curriculum
Where this fits
- British Columbia, Grade 2
Mathematics, Number: addition and subtraction to 100BC2-MA-11
The outcomes and strands follow the British Columbia curriculum.
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