Question

1) There is an auditorium with 25 rows of seats. There are 10 seats in the first
row, 12 in the second row, 14 seats in the third row and so on. Find
the number of seats in the 20th row and also find how many total
seats are there in the auditorium?​

Answer 1

Given :-

• Total rows in an auditorium = 25
• Seats in first rows = 10
• Seats in second rows = 12
• Seats in third row = 14

To Find :-

• Number of seats in 20th row ?
• How many seats are there in the auditorium ?

Solution :-

we know that,

• an = a + (n - 1)d
• sn = (n/2)[2a + (n - 1)d]

given that,

• a = 10
• d = 12 - 10 = 2

so,

→ a(20) = a + (20 - 1)d

→ a(20) = 10 + 19 * 2

→ a(20) = 10 + 38

→ a(20) = 48 seats (Ans.)

therefore,

→ s(25) = (25/2)[2*10 + (25 - 1)2]

→ s(25) = (25/2)[20 + 48]

→ s(25) = (25/2) * 68

→ s(25) = 25 * 34

→ s(25) = 850 (Ans.)

Hence, the number of seats in the 20th row are 48 seats and total seats in the auditorium are 850 .

Learn more :-

evaluate the expression given by

https://brainly.in/question/14081691

If the nth term of an AP is (2n+5),the sum of first10 terms is

https://brainly.in/question/23676839

Answer 2

Answer:

7sgdhdgrjir

Step-by-step explanation:

ioabsjsdbdh