The ratio of the number of books between A and B is 1:2. Now after putting some books into A, the ratio of A and B is 4:5. The number of books put into A is equal to the original two bundles. How much is the total.
甲、乙两捆书的本数比是1：2，现在往甲捆中放进一些书后，甲、乙两捆书的比是4：5，放进甲捆的书的本数是原来两捆书总数的多少．
<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(2/3) * (3/10)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>