1. **State the problem:** We need to calculate $1.2 \div 0.3$. 2. **Recall the division rule:** Dividing by a decimal can be simplified by multiplying numerator and denominator by the same power of 10 to make the divisor a whole number. 3. **Multiply numerator and denominator by 10:** $$\frac{1.2}{0.3} = \frac{1.2 \times 10}{0.3 \times 10} = \frac{12}{3}$$ 4. **Simplify the fraction:** $$\frac{\cancel{12}}{\cancel{3}} = 4$$ 5. **Final answer:** $$1.2 \div 0.3 = 4$$