Teacher Zhang and the students walked to plant trees together. They walked at a speed of 4km/h. One hour after departure, the school called to inform Teacher Zhang to return to school for a meeting within 10 minutes (including 10 minutes), and asked Teacher Zhang to wait at the same place. The school immediately Send someone to pick him up on a motorcycle. What is the minimum speed of the motorcycle to ensure that Mr. Zhang can attend the meeting on time?
张老师和学生们一起步行去植树，他们步行的速度是4km/h，出发1h后，学校打电话通知张老师在10min内(含10min)返校开会，并让张老师在原地等候，学校立即派人骑摩托车去接他，摩托车的速度至少是多大才能保证张老师按时参加会议？
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/6) / 2</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / (1/12)</gadget>
<output>12</output>

<gadget id="calculator">4 * 12</gadget>
<output>48</output>

<result>48</result>