Xiao Liang goes to the store to buy stationery. If he buys all the notebooks, he can buy 10 books. If he buys all the pencils, he can buy 15. Now he bought 4 notebooks first. How many pencils can he buy with the remaining money? ?
小亮去商店买文具，所需的钱如果全部买笔记本刚好可以买10本，如果全部买铅笔刚好可以买15枝，现在他先买了4本笔记本，剩下的钱还能买多少枝铅笔？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) * 4</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(3/5) / (1/15)</gadget>
<output>9</output>

<result>9</result>