Let's break down the two operations:

1) $\frac{1}{2} \div 3$:

Dividing by 3 is the same as multiplying by the reciprocal of 3, which is $\frac{1}{3}$.

So, we have:

$\frac{1}{2} \div 3 = \frac{1}{2} \times \frac{1}{3} = \frac{1 \times 1}{2 \times 3} = \frac{1}{6}$

Thus, $\frac{1}{2} \div 3 = \frac{1}{6}$.

2) $21 \div 3$:

This is a simple division:

$21 \div 3 = 7$

So, $21 \div 3 = 7$.

Final Answer:

• $\frac{1}{2} \div 3 = \frac{1}{6}$
• $21 \div 3 = 7$

Would you like further details or clarification on these operations?

Here are some related questions:

1. What is the result of $\frac{5}{6} \div 2$?
2. How do you convert division of fractions into multiplication?
3. What happens when you divide a fraction by a fraction?
4. How would you simplify the fraction $\frac{4}{12}$?
5. What are some applications of fractions in real-life scenarios?

Tip: When dividing fractions, always remember to multiply by the reciprocal of the divisor.