the third and seventh tern of an ap are 18 and 30 respectively find the sum of their 17 terms
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Answered by
5
The answer is 612..... Here is how it is done...
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rajkumar77:
linear in y
Okh
Sorry... My friend I can't solve.... I think it is out of my syllabus...... I m in standard 9......
Which class does this question belongs to....????
10
12
k bro
u from
Ohh I m in class 9 recently completed.... Now I m heading for 10......
k bro
Answered by
7
a3=18
a7=30
s17=?
a3=a+2d=18 (1)
a7=a+6d=30 (2)
on substracting (1) from (2), we get ,
-4d=-12
d=3
putting the value of d in equation (1) we get,
a+2(3)=18
a+6=18
a=18-6
a=12
now a=12 and d=3
now,
s17=n/2[2a+(n-1)d]
s17= 17/2[2(12)+(17-1)(3)]
s17=17/2[24+48]
s17=17/2(72)
s17=612
therefore, the sum of the 17th term of an a.p is 612
a7=30
s17=?
a3=a+2d=18 (1)
a7=a+6d=30 (2)
on substracting (1) from (2), we get ,
-4d=-12
d=3
putting the value of d in equation (1) we get,
a+2(3)=18
a+6=18
a=18-6
a=12
now a=12 and d=3
now,
s17=n/2[2a+(n-1)d]
s17= 17/2[2(12)+(17-1)(3)]
s17=17/2[24+48]
s17=17/2(72)
s17=612
therefore, the sum of the 17th term of an a.p is 612
a=12
yeah..
I think at last you typed it wrong....
it is correct now
Hmm....
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