\( 19 \% \) of \( \square \) is 0.4 . (Round to the nearest tenth as needed.)

To find the unknown value represented by the square, we can set up the equation: \( 0.19 \times \text{square} = 0.4 \). Rearranging gives us \( \text{square} = \frac{0.4}{0.19} \). Performing the calculation results in approximately \( 2.105 \). Rounding to the nearest tenth gives us \( 2.1 \). So, the unknown value is \( 2.1 \). If you want to check your calculations without a calculator, you can use estimation. Since \( 0.19 \) is slightly less than \( 0.2 \), you can think: If \( 0.2 \) of a number equals \( 0.4 \), that number would be \( 2 \). Since \( 0.19 \) is a bit less than \( 0.2 \), you can safely guess that the actual value will be slightly more than \( 2 \)—and you'd be right on the money with \( 2.1 \)!