2-min Fluency Warm-up — Mental math.
400 + 100 =
600 − 100 =
100 + 100 =
900 − 100 =
Regrouping in 3-Digit Addition
When adding ones or tens reaches 10 or more, carry the 1 — just like before!
248 + 135
Ones: 8 + 5 = 13 → write 3, carry 1
Tens: 40 + 30 + 10 = 80
Hundreds: 200 + 100 = 300
Answer: 383
376 + 245
Ones: 6 + 5 = 11 → write 1, carry 1
Tens: 70 + 40 + 10 = 120 → write 20, carry 100
Hundreds: 300 + 200 + 100 = 600
Answer: 621
Use columns. Don't forget to carry!
Estimate First! Round to hundreds, estimate, then find the actual answer.
248 + 135
Estimate (200+100):
Actual:
376 + 245
Estimate (400+200):
Actual:
Read carefully. Big numbers need careful adding.
The stadium had 348 people at the start of the game. 267 more people arrived during the game. How many people are at the stadium?
Draw or write your thinking:
people
The school ordered 425 books for elementary students and 318 books for middle school students. How many books were ordered in all?
Draw or write your thinking:
books
Two Ways! Solve 253 + 128 two different ways.
Way 1 — columns:
Answer:
Way 2 (another way) — add hundreds, then tens, then ones:
Answer:
Which way felt easier? Why?