Subtract Multiples of 10 from Multiples of 10

Students will subtract a multiple of 10 from another multiple of 10 within the range 10–90 using place value strategies and concrete models. Students recognize that the computation mirrors single-digit subtraction operating on tens.

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

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12 rungs. A star at the top.

60 − 60 =

How it is taught

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Tens subtract like ones, then keep zero ones.

A multiple of ten has zero ones.

Read it: Add or take away tens: jump 10 at a time

36 + 50: 50 is 5 tens. Jump 10, 5 times from 36: 46, 56, 66, 76, 86. To take 50 away, jump back: 86 − 50 = 36.

Say how many tens: 50 is 5 tens.
Jump 10 that many times: forward to add, back to take away.
Say where you land: 36 + 50 = 86, and 86 − 50 = 36.

Each jump of 10 changes the tens digit by 1.

The ones digit does not change, because no ones are added or taken: it stays 6.

So adding or taking away tens is counting by tens from the start.

Count by tens from the start, forward or back. The ones stay the same.

Adding 5 to the ones: 36 + 50 = 41.

50 is 5 tens, not 5 ones. Jump 10, 5 times: 86.

Start at 80 and jump back 10, 2 times. Where do you land? — 60. 70, 60. So 80 − 20 = 60.

70 − 30

Let's subtract seventy minus thirty. We can use a number line to count by tens.

Start at seventy. That's the same as seven tens.

Now we take away thirty. That means jumping back three tens.

We land on forty! So seventy minus thirty is forty.

We can also stack them. Write seventy on top and thirty below.

Start with the ones. Zero minus zero is zero.

Now the tens. Seven tens minus three tens is four tens.

Grade 1 · Subtracting tens just like single digits

Seventy minus thirty equals forty. Subtracting tens is just like subtracting single digits!

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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