From the five natural numbers 2, 11, 13, 29, and 47, take two numbers each time (one as the numerator and one as the denominator) to form a fraction. How many simple fractions can be formed in total?
从2、11、13、29、47这五个自然数中，每次取两个数(一个作分子、一个作分母)组成一个分数，一共可以组成多少个最简分数．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<result>20</result>