Use a number from 4, 5, and 6 as the numerator, and a number from 7, 8, and 9 as the denominator. How many fractions can be formed in total?
用4、5、6中选一个数字作分子，从7、8、9中选一个数字作分母，一共可以组成多少个分数．
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<result>9</result>