4th and 5th grade collect tree species. The fifth grade collected a total of 16.74 kilograms, 2.8 kilograms more than the fourth grade. How many kilograms were collected by the two grades?
四、五年级采集树种．五年级一共采集了16.74千克，比四年级多采了2.8千克，两个年级共采集了多少千克？
<gadget id="calculator">16.74 - 2.8</gadget>
<output>13.94</output>

<gadget id="calculator">13.94 + 16.74</gadget>
<output>30.68</output>

<result>30.68</result>