Each exercise book is 0.40 yuan, and each pencil is 0.32 yuan. The teacher asked Xiaohu to buy some exercise books and pencils, and the total price was exactly the 10 yuan given by the teacher. But Xiaohu confuses the number of exercise books with the number of pencils, and the result is 0.56 yuan, so how many exercise books did the teacher plan to ask Xiaohu to buy?
练习本每本0.40元，铅笔每支0.32元．老师让小虎买一些练习本和铅笔，总价正好是老师所给的10元钱．但小虎将练习本的数量与铅笔的数量记混了，结果找回来0.56元，那么老师原打算让小虎买多少本练习本．
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