Huanhuan and Lele went to buy exercise books. Huanhuan bought 4 and Lele bought 6. Huanhuan spent 1 yuan less than Lele. How much is an exercise book?
欢欢和乐乐去买练习本，欢欢买了4本，乐乐买了6本，欢欢比乐乐少花1元钱，一本练习本多少钱？
<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>