The distance between A and B is 3.6 kilometers. Two dogs run towards each other from A and B. They run 450 meters and 350 meters per minute respectively. After they ran towards each other for 1 minute, they turned around and ran back for 2 minutes at the same time, then turned around and ran towards each other for 3 minutes, and then turned around and ran back for 4 minutes, ... until they meet, how many minutes will it take from starting to meeting.
甲乙两地相距3.6千米，两条狗从甲、乙两地相向奔跑．它们每分钟分别跑450米和350米．它们相向跑1分钟后，同时调头背向跑2分钟，又调头相向跑3分钟，再调头背向跑4分钟，…，这样直到相遇为止，从出发到相遇需多少分钟．
<gadget id="calculator">450 + 350</gadget>
<output>800</output>

<gadget id="calculator">3_600 - 800</gadget>
<output>2_800</output>

<gadget id="calculator">800 * 2</gadget>
<output>1_600</output>

<gadget id="calculator">800 * 3</gadget>
<output>2_400</output>

<gadget id="calculator">1_600 - 2_400</gadget>
<output>-800</output>

<gadget id="calculator">800 * 4</gadget>
<output>3_200</output>

<gadget id="calculator">800 * 5</gadget>
<output>4_000</output>

<gadget id="calculator">3_200 - 4_000</gadget>
<output>-800</output>

<gadget id="calculator">800 * 6</gadget>
<output>4_800</output>

<gadget id="calculator">800 * 7</gadget>
<output>5_600</output>

<gadget id="calculator">4_800 - 5_600</gadget>
<output>-800</output>

<gadget id="calculator">2_800 + (-800) + (-800) + (-800)</gadget>
<output>400</output>

<gadget id="calculator">400 / 800</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">9 - (1/2)</gadget>
<output>17/2 = around 8.5</output>

<gadget id="calculator">1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + (17/2)</gadget>
<output>89/2 = around 44.5</output>

<result>89/2 = around 44.5</result>