An accountant is checking out. He found that there was an extra 21 yuan, 40 cents and 2 cents on the account. He recalled that the decimal point of a sum of money was wrongly counted.
一位会计在结账时．发现账面上多了21元4角2分，他回忆是把一笔钱数的小数点点错了一位，原来这笔钱是多少．
<gadget id="calculator">4 / 10</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">2 / 100</gadget>
<output>1/50 = around 0.02</output>

<gadget id="calculator">21 + (2/5) + (1/50)</gadget>
<output>1_071/50 = around 21.42</output>

<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">(1_071/50) / 9</gadget>
<output>119/50 = around 2.38</output>

<result>119/50 = around 2.38</result>