Find the pattern, and then fill in the numbers: 0.1, 0.3, 0.7, 1.3, how much.
找规律，再填数：0.1、0.3、0.7、1.3、多少．
<gadget id="calculator">0.1 + 0.2 + 0.4 + 0.6 + 0.8</gadget>
<output>2.1</output>

<result>2.1</result>