Determine the seating capacity of an auditorium with 18 rows of seats if there are 20 seats in the first row, 24 seats in the second row, and 28 seats in the third row and so on.

Question

anonymous · Answer

lol that's a weird auditorium. quarter circle.

anonymous · Answer

it has 20*18+4(1+2+3+...+17) seats

anonymous · Answer

= 20*18 +4(17*16)/2

anonymous · Answer

i'm sorry, do you think you can explain it? i just don't understand what you have to do.

anonymous · Answer

the capacity of the auditorium is 1102

anonymous · Answer

it's 972. sorry first answer is incorect

anonymous · Answer

the first row has 20 seats.
the second row has 24 seats and the third row has 28 seats and so on.
so it is
20+24+28+....
20+20+20+...+4+8+12...
20*18+4(1+2+3+...+17)
= 20*18 +4(17*18/2)

anonymous · Answer

= 972

anonymous · Answer

since 1+2+3+4+....+ n-1 +n = n(n+1)/2