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Add a Two-Digit Number and a One-Digit Number

Students will add a two-digit number and a one-digit number within 100 using strategies based on place value. Students practice adding to the ones place and regrouping (making a new ten) when necessary.

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Add a Two-Digit Number and a One-Digit Number

Grade 1 · Comparing and Computing with Two-Digit Numbers · question 1 of 3

0 of 12

12 rungs. A star at the top.

11 + 8 =

How it is taught

0:00 of 2:17

Add the ones first.

Ten ones make a new ten.

Read it: Add ones to a 2-digit number

36 + 7. 36 is 3 tens and 6 ones. 6 and 7 make 13 ones, and 10 of them make a new ten: 4 tens and 3 ones, 43.

  1. Split the number into tens and ones: 3 tens and 6 ones.
  2. Add the ones: 6 and 7 make 13 ones.
  3. 10 ones make a new ten: 4 tens and 3 ones, 43.

Only the ones are added, so the tens stay until the ones reach 10.

10 ones are the same as 1 ten, so they are bundled.

When the ones stay under 10, the tens do not change: 52 + 4 = 56.

Add the ones. 10 ones make a new ten.

Writing 313 for 3 tens and 13 ones.

13 ones is 1 ten and 3 ones: 4 tens and 3 ones, 43.

29 + 6 = ___ — 35. 9 and 6 make 15 ones: a new ten and 5. 35.

27 + 5

Maya has 27 stickers. Her friend gives her 5 more. How many does she have now?

Let's stack the numbers. Twenty-seven on top, five underneath, lined up in the ones column.

Start with the ones. What is seven plus five?

Twelve! But twelve is too big to fit in the ones place.

Ten ones make a new ten. We carry that ten over to the tens column.

27 stickers + 5 more = ?Adding a one-digit number to a two-digit number.27+57 + 5 = 12too big for one digit!12 = 1 ten + 2 ones123ANSWER32stickers
Grade 1 · Adding ones and making a new ten

Two ones are left over. Write a two in the ones place.

Now the tens. Two tens plus the new ten makes three tens.

Write a three in the tens place.

Twenty-seven plus five is thirty-two. Maya has thirty-two stickers!

What you see

While they climb, your page writes one true line to ask about tonight, and a short note each Sunday.

MayaGrade 3 · Mathematics
Did you know?

A chessboard has 64 squares — share them out between the 8 rows and each row holds exactly 8.

Today’s goal
1 star — one skill mastered, every rung of its ladder climbed
Climbing now
Divide within 100

An example student.

MayaGrade 3 · Mathematics

Maya earned 2 stars this week — Interpret multiplication as equal groups, which took 6 answers over 3 days before its star landed 3 days ago and Multiply by 6, 7, 8 and 9. Next up: Divide within 100.

An example week.

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