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Lesson · Grade 2 · Mathematics

Adding Two-Digit Numbers: Tens and Ones

  • Grade 2
  • Mathematics
  • 1 min 12 s
  • British Columbia
  • BC2-MA-09

To work out 48 + 37, children first estimate on a number line (about 50 + 40 = 90). Then they build both numbers from rods of ten and loose ones and add the tens (40 + 30 = 70), then the ones (8 + 7 = 15), to get 70 + 15 = 85. Ten ones snap into a new ten to show that 8 tens and 5 ones make 85, close to the estimate of 90.

Concept: Adding two-digit numbers with tens and ones

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In one sentence

The question this lesson answers

What is forty-eight plus thirty-seven? Let's find out.

Estimate first. Forty-eight is close to fifty.

Transcript

What the lesson says

What is forty-eight plus thirty-seven? Let's find out.

Estimate first. Forty-eight is close to fifty.

Thirty-seven is close to forty.

Fifty plus forty is ninety. So the answer is about ninety.

Forty-eight is four tens and eight ones.

Thirty-seven is three tens and seven ones.

Add the tens. Forty plus thirty is seventy.

Add the ones. Eight plus seven is fifteen.

Put them together. Seventy plus fifteen is eighty-five.

Ten ones snap together to make one ten.

Eight tens and five ones make eighty-five.

Eighty-five is close to ninety. Our answer makes sense.

Add the tens, then the ones. Forty-eight plus thirty-seven is eighty-five.

Curriculum

Where this fits

British Columbia, Grade 2

Mathematics, Number: addition and subtraction to 100BC2-MA-09

Previous: Subtracting by Counting UpNext: Adding with Friendly Numbers: 48 + 37

The outcomes and strands follow the British Columbia curriculum.

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