Students are active on the playground, the number is between 40-50, it is known that the ratio of the number of boys to the number of girls is 5:4, how many boys are active on the playground.
同学们在操场上活动，人数在40-50之间，已知男生人数与女生人数的比是5：4，在操场上活动的男生有多少人．
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">45 * (5/9)</gadget>
<output>25</output>

<result>25</result>