Question

find.the 12th term from the end of the AP 3,6,9......60

Answer 1

GIVEN:-

To find the 12th term from the end of the AP 3,6,9. . . . . .60

SOLUTION:-

a = 3 , d = 3 , A_n = 60

By using formula ,

A_n = a + ( n - 1 ) d

So, 60 = 3 + ( n - 1 ) 3

60 = 3 + 3n - 3

60 = 3n

n = 20

Total number of term is 20

And 12th term from end means 9 th term from beginning , by the formula ( n - 12 + 1 ) th term is the term from beginning is equal to given term from last

So, ( n - 12 + 1 )th term

= ( 20 - 12 + 1 )

= 9th term

So, A_n = 3 + ( 9 - 1 ) 3

= 3 + (8)×3

= 3 + 24

A_n = 27

Therefore,

27 is the 12th term from end and 9th term from beginning.

THANKS.