Using the sum of an arithmetic sequence concept, the total number of seats in the hall is 2604
The number of seats in a row increases by 2 per row :
Number of seats in row 1 = 65 - 2(22) = 65 - 44 = 21 seats
Number of seats in row 42 = 65 + 2(19) = 65 + 38 = 103 seats
Common difference = 2
Using the sum of nth term in a sequence :
Sn = n/2(a + l)
Sn = 42/2(21 + 103)
Sn = 21(21 + 103)
Sn = 21(124)
Sn = 2604
Therefore, the total Number of seats is 2604.
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