The fourth grade in Zhenhai Yale is doing morning exercises. They are arranged in 10 rows. There are equal numbers of people in each row. Pingping stands in a certain row. The fifth person is counted from the front, and the ninth person is counted from the back. How many people are there in the fourth grade? ．
镇海雅乐四年级做早操，共排成10行，每行人数相等，平平站在某一行中，从前面数过去是第五位，从后面数过来是第9位，四年级一共有多少人．
<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<gadget id="calculator">5 + 8</gadget>
<output>13</output>

<gadget id="calculator">13 * 10</gadget>
<output>130</output>

<result>130</result>