The express train and the slow train start from two places 540 kilometers apart at the same time, and run toward each other. They meet at 4 o'clock. It is known that the speed ratio of the express train and the slow train is 5:4. How many kilometers does the express train travel per hour?
快车和慢车同时从相距540千米的两地出发，相向而行，经过4时相遇，已知快车和慢车的速度比是5：4，快车每时行多少千米？
<gadget id="calculator">540 / 4</gadget>
<output>135</output>

<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">135 * (5/9)</gadget>
<output>75</output>

<result>75</result>