The distance between A and B is 42 kilometers. It takes 2.1 hours to ride a bicycle and 10.5 hours to walk. If a person walks from A to B for 4 hours and then changes to a bicycle, how many hours will he arrive at B land?
甲、乙两地相距42千米，骑车行完全程要2.1小时，步行要10.5小时，一个人由甲地到乙地先步行4小时后，改骑车，他还要几小时才能够到达乙地？
<gadget id="calculator">42 / 10.5</gadget>
<output>4</output>

<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">42 - 16</gadget>
<output>26</output>

<gadget id="calculator">42 / 2.1</gadget>
<output>20</output>

<gadget id="calculator">26 / 20</gadget>
<output>13/10 = around 1.3</output>

<result>13/10 = around 1.3</result>