Mrs. Zhang bought a teacher’s residence, and originally planned to pay by installments. One payment method is to pay 70,000 yuan in the first year, and 10,000 yuan a year thereafter; the other payment method is to pay 2 yuan a year for the first half of the time. RMB 10,000, and in the second half of the year, an annual payment of RMB 15,000. The total amount of payment and the payment time are the same for both payment methods. If you make a one-time payment, you can pay less than 16,000 yuan for the house. Now Mr. Zhang decided to adopt a one-time payment method. Question: How much does Mr. Zhang have to pay for the house?
张老师购买了一套教师住宅，原计划采取分期付款方式，一种付款方式是开始第一年先付7万元，以后每年付款1万元；另一种付款方式是前一半时间每年付款2万元，后一半时间，每年付款1万5千元．两种付款方式的付款总数和付款时间都相同．假如一次性付款，可以少付房款1万6千元．现在张老师决定采用一次性付款方式．问：张老师要付房款多少万元？
<gadget id="calculator">7 - 1</gadget>
<output>6</output>

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

<gadget id="calculator">(1/2) * 2</gadget>
<output>1</output>

<gadget id="calculator">(1/2) * 1.5</gadget>
<output>0.75</output>

<gadget id="calculator">0.75 - 1</gadget>
<output>-0.25</output>

<gadget id="calculator">1 + (-0.25)</gadget>
<output>0.75</output>

<gadget id="calculator">6 / 0.75</gadget>
<output>8</output>

<gadget id="calculator">8 - 1</gadget>
<output>7</output>

<gadget id="calculator">7 * 1</gadget>
<output>7</output>

<gadget id="calculator">7 - 1.5</gadget>
<output>5.5</output>

<gadget id="calculator">7 + 5.5</gadget>
<output>12.5</output>

<result>12.5</result>