Every time you make a call to a certain place for no more than 3 minutes, you have to pay 0.5 yuan. If it exceeds 3 minutes, an additional 0.3 yuan will be paid for every 1 minute exceeded. Xiao Ming made a call to a certain place and paid 1.70 yuan. How many minutes did he call?
打某地电话每次不超过3分钟要交0.5元．如果超过3分钟，每超过1分钟再交0.3元．小明打一次到某地的电话，交费1.70元，他打了几分钟？
<gadget id="calculator">1.7 - 0.5</gadget>
<output>1.2</output>

<gadget id="calculator">1.2 / 0.3</gadget>
<output>4</output>

<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<result>7</result>