Mom bought 5.5 kilograms of tomatoes in the supermarket, paid 20 yuan, and got back 2.4 yuan. How much is it per kilogram of tomatoes?
妈妈在超市买了5.5千克西红柿，付出20元，找回2.4元．每千克西红柿多少元？
<gadget id="calculator">20 - 2.4</gadget>
<output>17.6</output>

<gadget id="calculator">17.6 / 5.5</gadget>
<output>3.2</output>

<result>3.2</result>