There are 4 yellow balls and 3 red balls in a box (the size and shape of the yellow balls and the red balls are the same), if you touch a ball randomly, what is the probability of getting a yellow ball?
盒中有4个黄球、3个红球(黄球与红球的大小、形状一样)，从中任意摸一个球，摸出黄的可能性是多少．
<gadget id="calculator">4 + 3</gadget>
<output>7</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<result>4/7 = around 0.571429</result>