You can divide with basic facts and multiply by 10, 100 and 1,000. Put them together to divide numbers like $240 \div 6$ in your head.
Idea clave
Name the number in a bigger unit so a basic fact appears. $240$ is 24 tens, and 24 tens $\div 6 = 4$ tens, so $240 \div 6 = 40$. In the same way, $3{,}600 \div 9$ is 36 hundreds $\div 9$, which is 4 hundreds, or 400.
Por qué funciona
Sharing 24 ten-dollar bills among 6 people gives each person 4 ten-dollar bills: \$40. The unit (tens) stays the same while you share, just as 24 apples shared by 6 is 4 apples each.
Ejemplo resuelto: Tens
Find $240 \div 6$.
- $240$ is 24 tens.
- 24 tens $\div 6 = 4$ tens, because $4 \times 6 = 24$.
- 4 tens is 40.
Respuesta: $40$
Ejemplo resuelto: A fact that ends in zero
Find $3{,}000 \div 5$.
- 30 hundreds $\div 5 = 6$ hundreds, because $6 \times 5 = 30$.
- 6 hundreds is 600.
- Check: $600 \times 5 = 3{,}000$.
Respuesta: $600$
Error común
Dropping a zero, as in $3{,}000 \div 5 = 60$. Name the unit out loud ("6 hundreds") and multiply back to check: $60 \times 5 = 300$, not $3{,}000$.