Dongdong walks from home to school, and takes a bus when he comes back. It takes 25 minutes to go back and forth; if he walks both ways, it takes a total of 40 minutes. How long will it take if you travel both ways by car?
冬冬从家到学校，如果去是步行，回来时乘车，往返一次共用25分钟；如果往返都步行，一共需要40分钟．如果往返都乘车，一共要多少时间．
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">25 - 20</gadget>
<output>5</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<result>10</result>