A laser signal is sent from the earth to the moon, and the signal reflected from the moon is received after 2.56 seconds. It is known that the speed of light is 300,000 km/s. Calculate the distance from the moon to the earth at this time.
一次从地球上向月球发射激光信号，经过2.56秒收到从月球反射回来的信号．已知光速是30万千米/秒，算一算，这时月球到地球的距离是多少．
<gadget id="calculator">2.56 / 2</gadget>
<output>1.28</output>

<gadget id="calculator">30 * 1.28</gadget>
<output>38.4</output>

<result>38.4</result>