Example 1. Calculate $8 \frac{1}{7} + 43.8 - 13.947 + 0.00375$ ( $\frac{1}{7}$ is an exact number, all others are approximate numbers)
The number with the least decimal places is 43.8, so the other numbers only need to be truncated to the hundredth place, and the result is accurate to the tenth place.
$$
\begin{array}{l}
\frac{1}{7}+43.8-13.947+0.00375 \\
\approx 0.14+43.8-13.95 \approx 30.0
\end{array}
$$