The school bought 90 science and technology books for the sixth grade, and lent them to the first class and the second class respectively according to the ratio of 5:4, how many books were borrowed by the second class.
学校给六年级买来90本科技书，按5：4分别借给一班和二班，二班借多少本．
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

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

<gadget id="calculator">90 * (4/9)</gadget>
<output>40</output>

<result>40</result>