An auditorium has 20 seats on the first row, 24 seats on the second row, 28 seats on the third row and so on. The auditorium has 15 rows of seats.
How many seats are there in the auditorium?
Given:
n=____ d=____ a1=____
Sn= n/2 [2a1 + (n - 1) d]
S15= 15/2 [2(___)+ (15 - 1) ___]
S15= 15/2 (40 + ____)
S15= 1440/2
S15= ____
How many seats are there in the auditorium?
Given:
n=____ d=____ a1=____
Sn= n/2 [2a1 + (n - 1) d]
S15= 15/2 [2(___)+ (15 - 1) ___]
S15= 15/2 (40 + ____)
S15= 1440/2
S15= ____
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Answer:
n = 15, d = 4, a1 = 20
Sn = n/2 [2a1 + (n - 1) d]
S15 = 15/2 [2(20) + (15 - 1) 4]
S15 = 15/2 (40 + 56)
S15 = 15/2 (96)
S15 = 1440/2
S15 = 720