The average score of the mathematics test in Class 1 of the five years was 91.5 points. It was later discovered that when calculating the score, a classmate's score of 98 was mistakenly calculated as 89 points. After recalculation, the average score of the class is 91.7 points. How many students are there in Class 1 of the fifth year?
五年1班数学考试平均成绩是91.5分，事后发现计算成绩时把一位同学的98分误为89分计算了．经重新计算后，该班平均成绩是91.7分．五年1班一共有多少个学生．
<gadget id="calculator">98 - 89</gadget>
<output>9</output>

<gadget id="calculator">91.7 - 91.5</gadget>
<output>0.2</output>

<gadget id="calculator">9 / 0.2</gadget>
<output>45</output>

<result>45</result>