Add and Subtract Big Numbers
Aligned to 3.NBT.A.2 — Common Core State Standards for Mathematics.
What this lesson teaches
Line up numbers by place value: ones under ones, tens under tens, hundreds under hundreds. Add or subtract each column, and regroup when needed.
Worked examples
Example 1
Add 256 + 137. Ones: 6 + 7 = 13, write 3 and carry 1. Tens: 5 + 3 + 1 = 9. Hundreds: 2 + 1 = 3. The answer is 393.
Example 2
Subtract 504 − 267. You cannot take 7 from 4, and the tens are 0, so borrow from the hundreds first: 504 becomes 4 hundreds, 9 tens, 14 ones. The answer is 237.
Example 3
Line up by place, not by the left edge. Writing 45 under 300 so the 4 sits under the 3 gives a wrong answer every time.
Practice questions
- Solve 342 + 215.
- Solve 500 − 168.
- A store had 620 books and sold 145. How many are left?
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Sumar y Restar Números Grandes
Alinea los números por su valor posicional: unidades con unidades, decenas con decenas, centenas con centenas. Suma o resta cada columna y reagrupa cuando haga falta.
Ejemplo 1: Suma 256 + 137. Unidades: 6 + 7 = 13, escribe 3 y lleva 1. Decenas: 5 + 3 + 1 = 9. Centenas: 2 + 1 = 3. La respuesta es 393.
Ejemplo 2: Resta 504 − 267. No puedes quitarle 7 al 4, y las decenas son 0, así que primero pide prestado a las centenas: 504 se vuelve 4 centenas, 9 decenas y 14 unidades. La respuesta es 237.
Ejemplo 3: Alinea por valor posicional, no por la orilla izquierda. Escribir 45 debajo de 300 de modo que el 4 quede bajo el 3 da un resultado equivocado siempre.
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