Question

the first and the last term of an ap are 17 and 350 respective. if the cd is 9,how many terms are there and what is their sum

Answer 1

Answer:

38

6973

Step-by-step explanation:

Let say there are n term

an = a + (n-1)d

350 = 17 + (n-1)9

333 = (n-1)9

n-1 = 37

n = 38

Sum = (n/2)(a + L)

= (38/2)(17+350)

= 19× 367

= 6973

Answer 2

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.

:)