1. **State the problem:** Calculate the division $1899 \div 21$ using long division. 2. **Recall the division formula:** For numbers $a$ and $b$, division is $a \div b = q$ where $q$ is the quotient. 3. **Perform long division:** - Divide 18 (first two digits of 1899) by 21: 21 does not go into 18, so quotient digit is 0. - Take first three digits 189: 21 goes into 189 how many times? Calculate $\left\lfloor \frac{189}{21} \right\rfloor = 9$. - Multiply $9 \times 21 = 189$. - Subtract $189 - 189 = 0$. - Bring down the last digit 9. - Divide 9 by 21: 21 does not go into 9, so quotient digit is 0. 4. **Combine quotient digits:** The quotient is 90 with a remainder 9. 5. **Express remainder as decimal:** - Add decimal point and zero: remainder 9 becomes 90. - Divide 90 by 21: $\left\lfloor \frac{90}{21} \right\rfloor = 4$. - Multiply $4 \times 21 = 84$. - Subtract $90 - 84 = 6$. - Bring down zero: 60. - Divide 60 by 21: $\left\lfloor \frac{60}{21} \right\rfloor = 2$. - Multiply $2 \times 21 = 42$. - Subtract $60 - 42 = 18$. - Bring down zero: 180. - Divide 180 by 21: $\left\lfloor \frac{180}{21} \right\rfloor = 8$. - Multiply $8 \times 21 = 168$. - Subtract $180 - 168 = 12$. 6. **Stop here or continue for more decimals.** 7. **Final answer:** $$1899 \div 21 = 90.428...$$ Rounded to three decimal places, the quotient is $90.429$.