The father goes upstairs twice as fast as Xiaoqiang. It takes 2 minutes for Xiaoqiang to go from the first floor to the fourth floor. How many minutes does it take for his father to go from the first floor to the tenth floor?
父亲上楼的速度比小强快一倍，小强从一楼到四楼要2分钟，父亲从一楼到十楼要多少分钟．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">2 / 3 / 2</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">(1/3) * 9</gadget>
<output>3</output>

<result>3</result>