During the "May 1st" golden week, shopping mall A offered a "10% discount" discount, and shopping mall B offered a promotion in the form of "free 10 yuan shopping vouchers for orders over 100". Uncle Wang is going to buy clothes worth 420 yuan. Which shopping mall is the best one? How much money can you save?
"五一"黄金周，甲商场以"打九折"的措施优惠，乙商场以"满100送10元的购物券"的形式促销．王叔叔打算买420元的衣服，在哪家商场购物划算些？能省多少钱？
<gadget id="calculator">420 - 40</gadget>
<output>380</output>

<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">420 * (9/10)</gadget>
<output>378</output>

<gadget id="calculator">380 - 378</gadget>
<output>2</output>

<result>2</result>