The number of short students in the class is 2/5*400 = <<2/5*400=160>>160

The total number of short and tall students is 160+90 = <<160+90=250>>250

Since there are 400 students in the class, the number of students with average height is 400-250 = <<400-250=150>>150

# Answer

150
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
The number of short students in a class is 2/5 of the total number of students. If there are 90 tall students, and the class has 400 students, calculate the total number of students with average height.
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
150
The number of short students in a class is 2/5 of the total number of students. If there are 90 tall students, and the class has 400 students, calculate the total number of students with average height.
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