chapter :ap and gp
The first and the last term of an AP is 17 and 350 respectively. If the common difference
is 9 then, find the number of terms and what is their sum?
Answers
Answered by
2
Step-by-step explanation:
a=17, d=9, l=350
l=a+(n-1)d
from this we get ,n=38=no. of terms
sum=s=n/2(a+l)=19(17+350) =6973
hope this is useful
Answered by
3
Answer:
a = 17 , an = 350 , d = 9
an = a+(n - 1)d
350 = 17 + ( n - 1) 9
350 = 17 + 9n - 9
350 = 8 + 9n
350 - 8 = 9n
342 = 9n
n = 342/9
n = 38
Sn = n/2 {a + an }
S38 = 38/2 {17 + 350}
S38 = 19 {367}
S38 = 6973
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