Adding and Subtracting within 20

Aligned to 1.OA.C.6 — Common Core State Standards for Mathematics.

What this lesson teaches

We can add and subtract bigger numbers by using strategies: counting on, making a ten, or using a fact we already know.

Example 1

8 + 5: make a ten first. Take 2 from the 5 to make 8 into 10, leaving 3. 10 + 3 = 13.

Example 2

9 + 6: take 1 from the 6 to make 9 into 10, leaving 5. 10 + 5 = 15.

Example 3

15 − 7: count back from 15 in two hops — back 5 to reach 10, then back 2 more. That lands on 8.

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

Podemos sumar y restar números más grandes usando estrategias: contar hacia adelante, formar una decena o usar un dato que ya conocemos.

Ejemplo 1: 8 + 5: primero forma una decena. Toma 2 del 5 para convertir el 8 en 10, y te quedan 3. 10 + 3 = 13.

Ejemplo 2: 9 + 6: toma 1 del 6 para convertir el 9 en 10, y te quedan 5. 10 + 5 = 15.

Ejemplo 3: 15 − 7: cuenta hacia atrás desde 15 en dos saltos — 5 hacia atrás para llegar a 10, y luego 2 más. Caes en 8.

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