The school newly purchased 450 extra-curricular books, leaving 90 books in the library, and the rest will be distributed to the fourth, fifth and sixth grades according to the ratio of 2:3:4. How many books will be allocated to the sixth grade?
学校新购进450本课外书，图书室留下90本，其余的按2：3：4分给四、五、六年级，六年级分到多少本书？
<gadget id="calculator">450 - 90</gadget>
<output>360</output>

<gadget id="calculator">2 + 3 + 4</gadget>
<output>9</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">360 * (4/9)</gadget>
<output>160</output>

<result>160</result>