Insert 5 numbers between 19 and 91 so that these 7 numbers form an arithmetic progression. What is the sum of these 7 numbers?
在19和91之间插入5个数，使这7个数构成一个等差数列，这7个数的和是多少．
<gadget id="calculator">19 + 91</gadget>
<output>110</output>

<gadget id="calculator">7 / 2</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">110 * (7/2)</gadget>
<output>385</output>

<result>385</result>