Family Math Studio · Lesson guide Guía de la lección
Unit 2, Lesson 12: Multiply Decimals
Standard 6.NOS.3What students are learning Qué aprenden
Key idea: To multiply decimals, first multiply as if there were no decimal points. Then count how many digits come after the decimal point in both numbers together. Put the decimal point in the answer so it has that same number of digits after the point.Idea clave: Para multiplicar decimales, primero multiplica como si no hubiera puntos decimales. Luego cuenta cuántos dígitos hay después del punto decimal en los dos números juntos. Pon el punto decimal en la respuesta para que tenga esa misma cantidad de dígitos después del punto.
Words to know Palabras clave
- Multiply Decimals Multiplicar decimales
- Multiply as whole numbers. Then count the digits after the dot.
- Multiplica como enteros. Luego cuenta los dígitos después del punto.
- Product Producto
- The answer to a times problem.
- La respuesta de multiplicar.
- Decimal point Punto decimal
- The dot between whole numbers and parts.
- El punto que separa los enteros de las partes.
- Estimate Estimar
- An answer that is close, found without exact work.
- Una respuesta cercana, sin hacer el cálculo exacto.
- Place value Valor posicional
- What a digit is worth by where it sits.
- Lo que vale un dígito según dónde está.
- Decimal places Cifras decimales
- How many digits are after the dot.
- Cuántos dígitos hay después del punto decimal.
Sentence starters Frases para empezar
I know ___ because ___.
First, I ___. Then, I ___.
The answer is ___, so ___.
How we did it in class today Cómo lo hicimos hoy en clase
- I want 4.5 × 12.60, the cost of 4.5 meters at $12.60 each.
- First I multiply without points, like whole numbers: 45 × 1260 = 56,700.
- Now I count decimal places: 4.5 has 1, and 12.60 has 2, so 1 + 2 = 3 decimal places.
- I put the point 3 places from the right in 56,700: that gives 56.700, or $56.70.
- I check with an estimate: 5 × $13 = $65, and $56.70 is close, so my answer is reasonable.
Play with today's math Jueguen con las matemáticas
Interactive Lesson Model — This is the exact same interactive tool your student used in class today. Change the numbers and watch what happens!
Modelo interactivo de la lección — Esta es la misma herramienta interactiva que su estudiante usó en clase hoy. ¡Cambie los números y observe qué sucede!
Works on a phone, a tablet, or a computer. Nothing to install, nothing to sign in to.
Try this together Inténtenlo juntos
Pick one question to talk about. You don't need to do them all!
Match each expression to its product.
2.5 × 4
Check the answer
The answer is: 10
Take-home sheet Hoja para llevar a casa
Lesson 2.12: Print the sheet (PDF) · Answers and talk notes (PDF) · Edit it (Word)
Lección 2.12: Imprimir la hoja (PDF) · Respuestas y notas para conversar (PDF) · Editarla (Word)
If they get stuck... Si se traban...
Watch out for this: A common mistake in Multiply Decimals is counting decimal places from only one factor instead of adding the decimal places from BOTH factors. For example, in 0.4 × 0.06, a student multiplies 4 × 6 = 24, then places the decimal point using just one factor's place count (1 place), writing 0.24 instead of the correct answer: 0.4 has 1 decimal place and 0.06 has 2 decimal places, for a total of 3, so 24 becomes 0.024. Before you submit, count the decimal places in EACH factor separately and add them together — that total is how many decimal places belong in your final answer.
Try asking: "Can you show me how you got that? Did we miss a step?"
Pregunte: «¿Puedes mostrarme cómo lo hiciste? ¿Nos saltamos algún paso?» Hablar de las matemáticas en voz alta ayuda mucho.