Question

the first term of an AP is 5,the last term is 45 and the sum of all its terms is 400.find the number of terms and the common difference of the AP? ​

Answer 1

first term=5

last term=45

sum=n/2 (first term +last term)

400=n/2 (50)

n=16

now =

16th term =first term+15d

45=5+15d

40/15=d

Answer 2

Step-by-step explanation:

a = 5 , l = 45 , Sn = 400

Sn = n/2 (a+l)

400 = n/2(5+45)

400 = n(50)/2

=>> n = 16

last term = 16

=>> a+(n-1)d = 45

=>> 5+ 15d = 45

=>> 15d = 40

=>> d = 8/3