Teacher Li brings the money to buy volleyballs, and he can buy 10. If he buys tennis balls whose unit price is half that of volleyballs, how many can he buy?
李老师带的钱去买排球，可以买10个，如果买单价是排球一半的网球，可以买多少个．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

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

<gadget id="calculator">20 * 1</gadget>
<output>20</output>

<result>20</result>