Add and subtract within 1000 (grade 3) · lesson

Add place by place

💡 Add ones to ones, tens to tens, and hundreds to hundreds, and carry when a place gets 10 or more.

Line the numbers up so the places match. Start with the ones.

If a place adds up to 10 or more, keep the ones digit. Carry the 1 to the next place to the left.

🧠 Let's work it out

Find 158 + 267.

What do you think comes next?

💡 Subtract one place at a time, and trade from the next place when the top digit is too small.

Start with the ones. If the top digit is too small, take 1 from the next place and make it 10 more.

A zero has nothing to give. So go one more place left. 502 can be 4 hundreds, 9 tens, and 12 ones.

🧠 Let's work it out

Find 502 − 174.

What do you think comes next?

💡 To subtract, you can count up from the small number to the big one.

Subtracting asks how far apart two numbers are. You can count up to find that.

Jump to the next hundred first. Then jump the rest of the way. Add up the jumps.

🧠 Let's work it out

Find 600 − 238.

What do you think comes next?

💡 Change a number to a close, round number, then fix the answer.

198 is just 2 less than 200. Adding 200 is easy.

So add 200, then take away the 2 extra you added.

🧠 Let's work it out

Find 534 + 198.

What do you think comes next?

💡 When a story says one amount is more than another, find that amount before you add them together.

"Al has 35 more than Ty" means you add 35 to Ty's amount to get Al's amount.

If the story asks for both together, add the two amounts as a second step.

🧠 Let's work it out

Ty has 120 cards. Al has 35 more. How many in all?

What do you think comes next?