the first and last terms of an ap are 17 and 350 respectively if the common difference is 9 find how many terms are there and what is their sum
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Answered by
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Answer:
There are 38 terms in the given A.P. and their sum is 6973.
Step-by-step explanation:
Here
a = 17
tn = 350 and d = 9
For an A.P.
tn = a + ( n - 1 ) x d
Substitute the values and you get
350 = 17 + 9n - 9
342 = 9n
n = 342/9
n = 38
Therefore there are 38 terms in the given A.P.
For an A.P.
Sn = n/2 ( a + tn )
Substitute the values and you get
S38 = 38/2 ( 17 + 350 )
S38 = 19 x 367
S38 = 6973
Therefore there are 38 terms in the given A.P. and their sum is 6973.
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a=17,tn=350,d=9.
to find:n
soln
tn=a+(n-1)d
350=17+(n-1)9
350=17+9n-9
350=8+9n
350-8=9n
342=9n
n=38
Sn=n/2{2a+(n-1)d}
Sn=38/2{2(17)+(38-1)9}
Sn=19{34+(37)9}
Sn=19(34+333)
Sn=19(367)
S38=6973
to find:n
soln
tn=a+(n-1)d
350=17+(n-1)9
350=17+9n-9
350=8+9n
350-8=9n
342=9n
n=38
Sn=n/2{2a+(n-1)d}
Sn=38/2{2(17)+(38-1)9}
Sn=19{34+(37)9}
Sn=19(34+333)
Sn=19(367)
S38=6973
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