Multi-Digit Addition & Subtraction — Intro

How the lesson starts: Multi-Digit Addition & Subtraction — Intro

Hoot's big book delivery
Hello! Hoot the owl runs the treehouse library. He has 2,346 books. A truck brings 1,275 more! How many books now? Let's add and subtract big numbers!
Column by column
Line up the places, then start with the ones. Ones: 6 + 5 = 11, carry 1. Tens: 4 + 7 + 1 = 12, carry 1. Hundreds: 3 + 2 + 1 = 6. Thousands: 2 + 1 = 3. Hoot has 3,621 books!
Two borrows
Hoot has 8,352 books and lends out 3,618. Ones: 2 − 8? Not enough, so borrow: 12 − 8 = 4. Tens: 4 − 1 = 3. Hundreds: borrow again, 13 − 6 = 7. Thousands: 7 − 3 = 4. It's 4,734! Watch out: never flip to 8 − 2.