There are 5 weights of 1g, 2g, 3g, 5g and 10g, and 2 weights are selected from them. The weights can only be placed on one side of the balance when used. How many different masses can be weighed.
有1g、2g、3g、5g和10g5个砝码，从中选出2个砝码，使用时砝码只能放在天平的一边，能称出多少种不同的质量．
<gadget id="calculator">2 * 1</gadget>
<output>2</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<result>10</result>