There are four numbers A, B, C and D, each number is 0.35 greater than the previous number, A's number is 12.1, find the sum of these four numbers.
有甲、乙、丙、丁四个数，每个数都比前一个数大0.35，甲数是12.1，求这四个数的和．
<gadget id="calculator">12.1 + 0.35</gadget>
<output>12.45</output>

<gadget id="calculator">12.45 + 0.35</gadget>
<output>12.8</output>

<gadget id="calculator">12.8 + 0.35</gadget>
<output>13.15</output>

<gadget id="calculator">12.1 + 12.45 + 12.8 + 13.15</gadget>
<output>50.5</output>

<result>50.5</result>