There are 10 students in a class. The average age of 9 of them is 8 years. By how many years will this average increase if the tenth student is (quite strangely) 28 years old?
9 students have an average age of 8 years so the sum of their ages is 9*8 = <<9*8=72>>72 years
A tenth student who is 28 years old will make the sum 72+28 = 100 years
The new average age will be 100/10 = <<100/10=10>>10 years
This is 10-8 = <<10-8=2>>2 years higher than the previous average.
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