To find the value of \( 15.4 \times 2.5 \) using the given information that \( 154 \cdot 25 = 3,850 \), we can rewrite the multiplication in terms of the original values.
Notice that: \[ 15.4 = \frac{154}{10} \] \[ 2.5 = \frac{25}{10} \]
Now we can find \( 15.4 \times 2.5 \): \[ 15.4 \times 2.5 = \left(\frac{154}{10}\right) \times \left(\frac{25}{10}\right) = \frac{154 \times 25}{100} \]
Since we know that \( 154 \times 25 = 3,850 \), we can substitute that in: \[ 15.4 \times 2.5 = \frac{3,850}{100} = 38.50 \]
So the answer is: 38.50