Students in two classes in the sixth grade collected tree species. The first class had 45 students, and each person collected 0.13 kilograms. The second class, with 36 students, collected a total of 6.15 kilograms. How many kilograms did the two classes collect in total?
六年级两个班的学生采集树种，一班45人，每人采集了0.13千克，二班36人共采集6.15千克，两个班一共采集多少千克？
<gadget id="calculator">0.13 * 45</gadget>
<output>5.85</output>

<gadget id="calculator">5.85 + 6.15</gadget>
<output>12</output>

<result>12</result>