If a box of pears is sold at 1.6 yuan per kilogram, it will lose 9 yuan; if it is sold at 2.1 yuan per kilogram, it will make 6 yuan. If it does not make a profit or lose money, how much should it sell for per kilogram?
一箱梨，如果每千克1.6元卖，就会亏9元；如果按每千克2.1元卖，就会赚6元，如果不赚也不亏，每千克应卖多少元？
<gadget id="calculator">9 + 6</gadget>
<output>15</output>

<gadget id="calculator">2.1 - 1.6</gadget>
<output>0.5</output>

<gadget id="calculator">15 / 0.5</gadget>
<output>30</output>

<gadget id="calculator">30 * 1.6</gadget>
<output>48</output>

<gadget id="calculator">48 + 9</gadget>
<output>57</output>

<gadget id="calculator">57 / 30</gadget>
<output>19/10 = around 1.9</output>

<result>19/10 = around 1.9</result>