Question

The first and the last term of an A.P. are 17 and 350 respectively. If the common difference is 9, how many terms are there and what is their sum?

Answer 1

Answer:

There are 38 number of terms and sum of these terms are 6973.  

Step-by-step explanation:

Given :  

First term, a = 17, last term , l = 350, common Difference , d = 9

By using the formula , l = a + (n - 1) d

350 = 17 + (n - 1) 9

350 - 17 = 9 (n -1)

333/9 = n - 1

37 = n - 1

n = 37 + 1

n = 38

By using the formula ,Sum of nth terms , Sn = n/2(a + l)

Sn = 38/2(350 + 17)

Sn = 19 (367)  

Sn = 6973

Hence, there are 38 number of terms and sum of these terms are 6973.  

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Answer 2

Step-by-step explanation:

an=350 a=17 d=9

an=a+(n-1)d

350=17+(n-1)9

350-17=(n-1)9

333=(n-1)9

333/9=n-1

37=n-1

n=38

number of terms 38

sn=n/2(a+an)

sn=38/2(17+350)

sn=19(367)

sn=6973