Adding and Subtracting within 20

Aligned to 2.OA.B.2 — Common Core State Standards for Mathematics.

What this lesson teaches

Use quick tricks to add and subtract small numbers in your head. Making a 10 helps a lot.

Example 1

8 + 5: first make 10 by taking 2 from the 5 (8 + 2 = 10), then add the leftover 3: 10 + 3 = 13.

Example 2

14 − 6: take 4 off first to land on 10, then take 2 more. That leaves 8.

Example 3

7 + 7 = 14 is a double you can memorize. Then 7 + 8 is just one more: 15.

Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.

Usa trucos rápidos para sumar y restar números pequeños de memoria. Formar un 10 ayuda mucho.

Ejemplo 1: 8 + 5: primero forma 10 quitando 2 al 5 (8 + 2 = 10), luego suma el 3 que sobra: 10 + 3 = 13.

Ejemplo 2: 14 − 6: quita primero 4 para llegar a 10, y luego quita 2 más. Quedan 8.

Ejemplo 3: 7 + 7 = 14 es un doble que puedes memorizar. Entonces 7 + 8 es solo uno más: 15.

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