How many different ways are there to take 2 different numbers from the 10 numbers from 1 to 10 so that their product is an even number?
从1～10这10个数中取出2个互异的数，使得它们的乘积是偶数，共有多少种不同的取数方法．
<gadget id="calculator">5 * 9</gadget>
<output>45</output>

<result>45</result>