A 900-meter-long road is built, and the ratio of the repaired to the unrepaired is 5:4. How many meters are not repaired?
修一段长900米的公路，已修的和未修的比是5：4，有多少米未修．
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">900 / 9</gadget>
<output>100</output>

<gadget id="calculator">100 * 4</gadget>
<output>400</output>

<result>400</result>