In the ancient country, Xiao Chunxiang met Liang Long. Xiao Chunxiang found that it took 9 seconds from touching Liang Long's head to leaving Liang Long's tail, and Liang Long completely waded a 60-meter-wide river. If it took 29 seconds (from the head entering the river to the tail leaving the river), how long is this Diplodocus long?
在远古之国，小春香遇到梁龙，小春香发现，从碰到梁龙的头到离开梁龙的尾巴，经过了9秒，而梁龙完全趟过一条宽60米的河，一共用了29秒(从头入河到尾巴离开河)，那么这条梁龙长多少米．
<gadget id="calculator">29 - 9</gadget>
<output>20</output>

<gadget id="calculator">60 / 20</gadget>
<output>3</output>

<gadget id="calculator">3 * 9</gadget>
<output>27</output>

<result>27</result>