口算

| $25+125=$ | $127+268 \approx$ | $285+125=$ | $370+250=$ | $250+250=$ |
| :--- | :--- | :--- | :--- | :--- |
| $320-160=$ | $520-340=$ | $750-360=$ | $823-199 \approx$ | $340-170=$ |
$25+125=150 \quad 127+268 \approx 400 \quad 285+125=410 \quad 370+250=620$

$250+250=500$

$$
\begin{array}{lllll}
320-160=160 & 520-340=180 & 750-360=390 & 823-199 \approx 620 & 340-170=170
\end{array}
$$