Question

Hey there buddies wanna help....
The first and last terms of an AP are 17 and 350 respectively. If the common difference is 9, how many terms are there and what is their sum​

Answer 1

Step-by-step explanation:

No of terms =38

Sum=38{2*17+(38-1)9}/2

Answer 2

Answer:

n=38

Sn=6973

Step-by-step explanation:

Hi ,

let a and d are first term and common  

difference for an AP.

number of terms of AP = n

last term = nth term = l = an

a = 17 , d = 9 ,

l = 350

a + ( n - 1 ) d = 350

17 + ( n - 1 ) 9 = 350

( n - 1 ) 9 = 350 - 17

( n - 1 ) 9 = 333

n - 1 = 333 / 9

n - 1 = 37

n = 37 + 1  

n = 38

Therefore ,

number of terms in given AP = n = 38

sum of n terms of AP = Sn

Sn = n /2 ( a + l )

here n= 38

S38 = 38 / 2 [ 17 + 350 ]

= 19 × 367

= 6973

I hope this helps you.

:)