Math, asked by ayushi6390, 1 year ago

the first and the 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?

Answers

Answered by Maximus
3
An=a+(n-1)d( by using this we can find the solution)
Given
An= 350
a=17
d=9
n=¿

so just put the value
350=17+(n-1)9
350-17=9n-9
333=9n-9
333+9=9n
342=9n
342÷9=n
38=n

show the number of term is 38
Sn = n/2(a+an)
sn=38/2(350+17)
Sn=19(367)
Sn=6973

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Answered by Panzer786
3
Hello !




First term ( A ) = 17



Common difference ( D ) = 9




Last term ( Tn ) = 350



A + ( N - 1 ) × d = 350




17 + ( n - 1 ) × 9 = 350



17 + 9n - 9 = 350



9n = 350 - 8



n = 342/9



n = 38



Number of terms = 38.




Sn = N/2 × [ 2A + ( n -1 ) × D ]



S38 = 38/2 × [ 2 × 17 + ( 38 - 1 ) × 9 ]





=> 19 ( 34 + 333)




=> 19 × 367



=> 6973.
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