Put together 4 squares with a perimeter of 21 cm to form a rectangle, what is the perimeter of the rectangle in cm?
把4个周长都是21厘米的正方形拼成一个长方形，长方形的周长是多少厘米．
<gadget id="calculator">21 / 4</gadget>
<output>21/4 = around 5.25</output>

<gadget id="calculator">(21/4) * 10</gadget>
<output>105/2 = around 52.5</output>

<result>105/2 = around 52.5</result>