The product of two factors is 0.645, one of which has one decimal place and the other has at least how many decimal places.
两个因数的积是0.645，其中一个因数是一位小数，另一个因数至少有多少位小数．
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<result>2</result>