Multiplication and division are opposites. One undoes the other. If you multiply $3$ by $4$ to get $12$, then dividing $12$ by $4$ takes you back to $3$. Because of this, every multiplication fact gives you matching division facts.
Fact families. Three numbers that multiply and divide together make a fact family. For $3$, $4$ and $12$:
| Multiplication | Division |
|---|---|
| $3\times4=12$ | $12\div3=4$ |
| $4\times3=12$ | $12\div4=3$ |
Use your times tables to divide. To work out $42\div7$, just ask: "$7$ times what is $42$?" Since $7\times6=42$, the answer is $42\div7=6$. So learning the tables well makes division quick.
Check your division by multiplying back. To check $36\div6=6$, multiply: $6\times6=36$ — correct! This is the easiest way to be sure a division answer is right.
Why it helps: you do not need to learn division facts separately — they come free with the multiplication facts you already know.
Common mistake: getting the family the wrong way round. From $5\times6=30$ the divisions are $30\div5=6$ and $30\div6=5$, never $5\div30$.