Two students, A and B, typed a document together. A typed 18 characters per minute, and B typed 22 characters per minute. The two students spent 30 minutes typing this document. How many characters are there in total?
甲、乙二位同学合打一份资料，甲每分打18个字，乙每分打22个字，两人用了30分打完这份资料，这份资料一共有多少个字？
<gadget id="calculator">18 + 22</gadget>
<output>40</output>

<gadget id="calculator">40 * 30</gadget>
<output>1_200</output>

<result>1_200</result>