1. **State the problem:** Evaluate the expression $9 \circ 0.4 \sqrt{0.019}$ where $\circ$ denotes multiplication. 2. **Recall the formula:** Multiplication is associative and commutative, so we can write the expression as $9 \times 0.4 \times \sqrt{0.019}$. 3. **Calculate the square root:** $$\sqrt{0.019} \approx 0.1377$$ 4. **Multiply the numbers step-by-step:** $$9 \times 0.4 = 3.6$$ $$3.6 \times 0.1377 \approx 0.4957$$ 5. **Final answer:** $$9 \circ 0.4 \sqrt{0.019} \approx 0.4957$$ This means the value of the expression is approximately 0.4957.