Advertisement Remove all ads

There Are 25 Rows of Seats in an Auditorium. the First Row is of 20 Seats, the Second of 22 Seats, the Third of 24 Seats, and So On. How Many Chairs Are There in the 21st Row ? - Algebra

Advertisement Remove all ads
Advertisement Remove all ads
Advertisement Remove all ads

There are 25 rows of seats in an auditorium. The first row is of 20 seats, the second of 22 seats, the third of 24 seats, and so on. How many chairs are there in the 21st row ?

Advertisement Remove all ads

Solution

The arrangement of chairs is 20, 22, 24, 26, ..........
Which  is an A. P.
Here, a = 20, d = 2. We want to find t21
tn = a + (n-1)d
∴ t21 = 20 + (21-1) × 2
          = 20 + 40
          = 60
∴  There are 60 chairs in the 21st row. 

Concept: Sum of First n Terms of an AP
  Is there an error in this question or solution?
Advertisement Remove all ads
Share
Notifications

View all notifications


      Forgot password?
View in app×