GRADE 2 · ALBERTAOUTCOME AB-MAT2-N2
L7 · Adding and subtracting lengths; problem-solving clinic
Learning goal
“I can solve problems about lengths in centimetres: joining lengths, finding how much is left, and two-step problems - and I choose the operation by reading the story.”
Centimetre — a unit for measuring length, written cm. A fingernail is about 1 cm wide.
Length — how long something is, from one end to the other.
Total — the whole amount when parts join. Joining lengths gives a total length.
Left — what remains after part of a length is cut or used.
Worked example
A red ribbon is 46 cm long. A blue ribbon is 38 cm long. How long are they together? Step 1 - READ THE STORY: the ribbons join end to end, so we add. Step 2 - ADD WITH PARTS: tens 40 + 30 = 70; ones 6 + 8 = 14; join: 70 + 14 = 84. Step 3 - NAME THE UNIT: the answer is a length: 84 cm.
Check yourself — explain it
Why is the answer written with 'cm'?
Paired problem — example still visible
A string is 57 cm. A second string is 29 cm. How long together? -> 86 cm (70 + 16)
Faded completion — last step is yours
A board is 64 cm. A strip is 27 cm. Together: 64 + 27 = ___ cm -> 91 cm
Ready to practise?
10 scored questions with a 3-rung hint ladder. Mastery needs 8/10 plus both gate questions.