The sum of each digit of a three-digit number is 10, and the numbers on each digit are different. How many such three-digit numbers are there?
一个三位数的各个数位的数字和为10，且各个数位上的数字各不相同，这样的三位数共有多少个．
<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">6 * 4</gadget>
<output>24</output>

<gadget id="calculator">16 + 24</gadget>
<output>40</output>

<result>40</result>