Grandpa Wang's family raised giant high-yielding long-haired rabbits. The rabbit house has 4 floors, and each floor has 15 rabbits. The average annual output of rabbit hair per rabbit is 0.821 kg. How many kilograms of rabbit hair does Grandpa Wang's family produce in one year?
王爷爷家养了巨型高产长毛兔，兔舍有4层，每层有15只．平均每只兔年产兔毛0.821千克．王爷爷家一年共产兔毛多少千克？
<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<gadget id="calculator">0.821 * 60</gadget>
<output>49.26</output>

<result>49.26</result>