The distance between A and B is 600 kilometers. At 8 o'clock in the morning, the passenger car drives to B at a speed of 60 kilometers per hour, and the truck drives from B to A at a speed of 50 kilometers per hour. Meet at the midpoint, what time in the morning does the van have to leave?
甲乙两地相距600千米，上午8时，客车以每小时60千米的速度开往乙地，货车每小时行50千米的速度从乙地开往甲地，要使两车在全程的中点相遇，货车必须在上午几时出发？
<gadget id="calculator">600 / 2 / 50</gadget>
<output>6</output>

<gadget id="calculator">600 / 2 / 60</gadget>
<output>5</output>

<gadget id="calculator">6 - 5</gadget>
<output>1</output>

<gadget id="calculator">8 - 1</gadget>
<output>7</output>

<result>7</result>