Two people, A and B, bind a batch of books. A binds 560 books per hour, and B binds 650 books per hour. A binds 450 books first and then B starts binding. How many hours after B's binding, the number of books bound by the two is equal?
甲、乙两人装订一批书，甲每小时装订560本，乙每小时装订650本，甲先装订450本后乙才开始装订．乙装订几小时后，两人装订的本数相等？
<gadget id="calculator">650 - 560</gadget>
<output>90</output>

<gadget id="calculator">450 / 90</gadget>
<output>5</output>

<result>5</result>