Answer:
The average of students in the two classes who went on the field trip is [tex] \frac{17}{20} [/tex].
Step-by-step explanation:
Average = [tex] \frac{sum \: \: of \: \:observations }{no. \: \: of \: \:observations} [/tex]
Average of students in the two classes =
[tex] \frac{ \frac{4}{5} + \frac{9}{10} }{2} [/tex]
[tex] \frac{ \frac{8+9 }{ 10} }{2} [/tex]
[tex] \frac{ \frac{17}{10} }{2} [/tex]
[tex] \frac{17}{20} [/tex]