Question

An auditorium has 40 rows of seats. There are 20 seats in the first row, 21 seats in the second row, 22 seats in the third row, and so on. Using relevant theories, find how many seats are there in all 40 rows?

S= n (a1+an ) / 2

S=20 (20+39) / 2

10 * (59)
Answer = 590 seats.

Is this answer correct

Answer 1

I think this is the wrong u hv to put an = 40

Then ur ans is 600