1. **State the problem:** Arrange the numbers $0.19 \times 10^4$, $0.019 \times 10^3$, $1.9 \times 10^2$, and $10.9 \times 10^3$ from smallest to largest. 2. **Recall the rule:** To compare numbers in scientific notation, convert them to standard decimal form or express all with the same power of 10. 3. **Convert each number:** - $0.19 \times 10^4 = 0.19 \times 10000 = 1900$ - $0.019 \times 10^3 = 0.019 \times 1000 = 19$ - $1.9 \times 10^2 = 1.9 \times 100 = 190$ - $10.9 \times 10^3 = 10.9 \times 1000 = 10900$ 4. **Order the numbers:** $19 < 190 < 1900 < 10900$ 5. **Final answer:** The numbers in order from smallest to largest are: $$0.019 \times 10^3, 1.9 \times 10^2, 0.19 \times 10^4, 10.9 \times 10^3$$