Latest Capgemini Aptitude Question SOLUTION: The sum of third and ninth term of an A.P is 8. Find the sum of the first 11 terms of the progression. 44 22 19 None of the above

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The sum of third and ninth term of an A.P is 8. Find the sum of the first 11 terms of the progression.

44
22
19
None of the above

Asked In Capgemini Anshul Shrivastava (9 years ago)

Unsolved Read Solution (5)

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Read Solution (5) :

Prabhu  (9 years ago)

The third term t3 = a + 3d
The ninth term t9 = a + 8d
t3 + t9 = 2a + 10d = 8

Sum of first 11 terms of an AP is given by
=11/2(2a+10d)
=11/2(8)
=88/2
=44

Is this solution Helpfull? Yes (29) | No (5)  

kapil sharma  (9 years ago)

a3 + a9 = 8
[a1 + (3-1)d] + [a1+ (9-1)d] = 8
2a1 + 10d = 8------------------(1)

Sum of first 11 terms-
S11= 11/2 * [2a1+(11-1)d]
S11= 11/2 * 8-----------(from 1)
S11=44

Is this solution Helpfull? Yes (14) | No (1)  

Raghavendar  (7 years ago)

Third term = a + 2d
ninth term = a + 8d
sum of two terms is equal to 8 i.e..., 2a+10d = 8
take two common i.e.., a + 5d =4 ------- (1)
first 11 terms is a,a+d,a+2d,a+3d,a+4d,a+5d,a+6d,a+7d,a+8d,a+9d,a+10d.
sum of the first 11 terms is 11a+55d
take 11 common 11(a+5d)----->(2)
sub (1) in (2)
we get answer 44

Is this solution Helpfull? Yes (3) | No (1)  

NISHANT AGARWAL  (9 years ago)

Formula
Sum=n/2 (2a + (n-1)d)
therefore , 3/2 (2a + (3-1)d) = 9/2 (2a+(9-1)d)
=3/2 (2a + 2d) = 9/2 (2a + 8d)
=3a+3d = 9a + 36d
=> 6a = - 33d
=> a = - 11/2 d

Now Sum of 11th term = 11/2 ( 2a + (n-1) d)
= 11/2 (2 x (-11/2)d + 10 d)
= 11/2 (-11d + 10d )
= 11/2 (-d) (Ans)

Is this solution Helpfull? Yes | No (6)  

hunny  (8 years ago)

Sum=n2(a+l) as a+l=8(given)
For 3 to 9 sum is (7/2(8)=28)
22 19 two r lesser than 28 .
so 44 answer.

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