A kind of salt water, the ratio of salt to water is 1:9, how many grams of salt should be added to prepare such a cup of 90 grams of salt water?
一种盐水，盐与水的比是1：9，要调制这样一杯90克的盐水，需要放盐多少克？
<gadget id="calculator">1 + 9</gadget>
<output>10</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">90 * (1/10)</gadget>
<output>9</output>

<result>9</result>