1. **Stating the problem:** Calculate $210 \div 5$ using long division. 2. **Formula and rules:** Division is splitting a number into equal parts. Here, we divide 210 by 5. 3. **Step-by-step long division:** - Divide 21 (from 210) by 5, which goes 4 times because $5 \times 4 = 20$. - Subtract 20 from 21, remainder is 1. - Bring down the next digit 0, making 10. - Divide 10 by 5, which goes 2 times because $5 \times 2 = 10$. - Subtract 10 from 10, remainder is 0. 4. **Intermediate work:** $$\begin{array}{r|l} 5 & 210 \\ & -20 \\ & \underline{10} \\ & -10 \\ & 0 \end{array}$$ 5. **Answer:** The quotient is $42$. Thus, $210 \div 5 = 42$.