The school proposed to donate books for the hand-in-hand activity, and pack the donated books into packs of 50 books. It is known that the fifth grade donated 12 packs, and the sixth grade donated 15% more than the fifth grade. How many books did the sixth grade donate?
学校提为手拉手活动捐书，并把捐来的书每50本打一包，已知五年级捐了12包，六年级比五年级多捐15%，六年级捐了多少本书？
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">1 + (3/20)</gadget>
<output>23/20 = around 1.15</output>

<gadget id="calculator">50 * 12 * (23/20)</gadget>
<output>690</output>

<result>690</result>