Xiaopang’s mother went to buy apples and wanted to buy 5 kilograms. When she paid, she found that it was 3 yuan and 50 cents less. In the end, she bought 4 kilograms, and there was 1 yuan and 50 cents left. How much money did the chubby mother bring in total?
小胖的妈妈去买苹果，想买5千克，付钱时发现还少3元5角，结果买了4千克，又剩下1元5角，小胖妈妈一共带了多少元钱．
<gadget id="calculator">3.5 + 1.5</gadget>
<output>5</output>

<gadget id="calculator">5 - 4</gadget>
<output>1</output>

<gadget id="calculator">5 / 1</gadget>
<output>5</output>

<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<gadget id="calculator">20 + 1.5</gadget>
<output>21.5</output>

<result>21.5</result>