Question

the first term of an ap are 17 and 350 respectively if common difference is 9 how many times are there in AP and find their sum

Answer 1

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.

:)

Answer 2

$\bf\huge\boxed{\boxed{\bf\huge\:Hello\:Mate}}}$

$\bf\huge Let\: a\: first\: terms\: and\: CD\: be\: D \:and\: L\: be\: last\: term$

$\bf\huge a = 17 , L = a_{n} = 350 and D = 9$

$\bf\huge According\:to\:the\:Question$

$\bf\huge => a_{n} = l = 350$

$\bf\huge => a + (n - 1)d = 350$

$\bf\huge => 17 + (n - 1)9 = 350$

$\bf\huge => 9(n - 1) => 350 - 17 = 333$

$\bf\huge => n - 1 = \frac{333}{9} = 37$

$\bf\huge => n = 37 + 1 = 38$

$\bf\huge Substitute\:a = 17 , l = 350 \:and\: n = 38$

$\bf\huge S_{n} = \frac{N}{n}(a + l)$

$\bf\huge S_{38} = \frac{38}{2}(17 + 350)$

$\bf\huge = 19\times 367$

$\bf\huge = 6973$

$\bf\huge\boxed{\boxed{\:Regards=\:Yash\:Raj}}}$