Mom sewed two pieces of the same square tablecloth into a large tablecloth, and sewed a circle of lace around it. It is known that the circumference of the square tablecloth is 28 decimeters. How many decimeters are there in total?
妈妈把两块同样的正方形台布缝成一块大台布，又在周围缝了一圈花边，已知正方形台布周长为28分米，花边一共有多少分米？
<gadget id="calculator">28 / 4</gadget>
<output>7</output>

<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<gadget id="calculator">14 + 7</gadget>
<output>21</output>

<gadget id="calculator">21 * 2</gadget>
<output>42</output>

<result>42</result>