Uncle Zhang raised a total of 90 chickens and ducks. It is known that the ratio of chickens to ducks is 5:4. How many chickens did Uncle Zhang raise?
张大爷养鸡和鸭共90只，已知养的鸡和鸭的比是5：4，张大爷养了多少只鸡？
<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">90 * (5/9)</gadget>
<output>50</output>

<result>50</result>