Mom bought a scarf worth 39.5 yuan with 50 yuan. She used the remaining money to buy a bottle of mineral water for 50 cents a bottle. How many bottles can she buy?
妈妈带50元钱买了一件价值39.5元的围巾，她用剩下的钱买5角钱一瓶的矿泉水，可以买多少瓶．
<gadget id="calculator">50 - 39.5</gadget>
<output>10.5</output>

<gadget id="calculator">10.5 / 0.5</gadget>
<output>21</output>

<result>21</result>