A bookbinding team had to bind 1820 books, and 315 books were bound in 4.5 hours. According to this calculation, how many hours will it take for the remaining books to be bound?
一个装订小组要装订1820本书，4.5小时装订了315本．照这样计算，剩下的书还需要多少小时才能装订完？
<gadget id="calculator">1_820 - 315</gadget>
<output>1_505</output>

<gadget id="calculator">315 / 4.5</gadget>
<output>70</output>

<gadget id="calculator">1_505 / 70</gadget>
<output>43/2 = around 21.5</output>

<result>43/2 = around 21.5</result>