The fifth and sixth graders collected tree species, the fifth grade collected 14.4 kg, and the sixth grade collected 3.9 kg less than the fifth grade. How many kilograms did the fifth and sixth grade students collect in total?
五、六年级同学采集树种，五年级采集了14.4千克，六年级比五年级少采集3.9千克．五、六年级同学一共采集多少千克？
<gadget id="calculator">14.4 - 3.9</gadget>
<output>10.5</output>

<gadget id="calculator">10.5 + 14.4</gadget>
<output>24.9</output>

<result>24.9</result>