The first term of A.P. is 5 and the last term is 45.and the sum of all its terms is 400.Find the number of the terms and the common difference of the A.P.

Asked by Sanjusanjanna22 | 12th Sep, 2019, 11:59: PM

Expert Answer:

According to the question,
 
a = 5, last term = l = 45, Sn = 400
Sn = n/2 (a + l)
400 = n/2 (5 + 45)
solving we get n = 16
using t16 = 45
a + 15d = 45
5 + 15d = 45
d = 8/3

Answered by Sneha shidid | 13th Sep, 2019, 09:32: AM