Question

Which term of the AP 1,8,13,18.....is 78​

Answer 1

16th term of A.P : 3,8,13,18,is 78.

a=3           d= 8-3 = 5              n=?  

= a+ (n-1)d

⇒78 = 3 + (n-1)5

⇒75 = (n-1)5

⇒n-1 = 15

⇒n = 16

∴78 is the 16th term of the given A.P.