Latest Dell Aptitude Question SOLUTION: Q. The sum of 3rd and 15th elements of an arithmetic progression is equal to the sum of 6th, 11th and 13th elements of the same progression. Then which element of the series should

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(#M40003430) DELL Numerical Ability question Terms in series Keep an EYE

Q. The sum of 3rd and 15th elements of an arithmetic progression is equal to the sum of 6th, 11th and 13th elements of the same progression. Then which element of the series should necessarily be equal to zero?

Option
a) 1
b) 9
c) 12
d) None

Asked In Dell Sulekha (12 years ago)

Solved Dr.Dipin Singh Read Solution (6)

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Read Solution (6) :

Dr.Dipin Singh  (12 years ago)

12

If we consider the third term to be ‘x”
The 15th term will be (x + 12d)
6th term will be (x + 3d)
11th term will be (x + 8d) and
13th term will be (x + 10d).
Thus, as per the given condition, 2x + 12d = 3x + 21d.Or x + 9d = 0.
x + 9d will be the 12th term.

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raju  (8 years ago)

first term=a+0d
2nd term=a+d;
lly 3rd term=a+2d

so according to question:
a+2d+a+14d=a+5d+a+10d+a+11d
2a+16d=3a+26d
a+11d=0
i.e 12 term = zero...

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Dr. Divya  (12 years ago)

12

Really nice solution given by Dipin.

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shesharaupally jyothi  (8 years ago)

12: as as by solving that we get a+11d=0,this implies that 12th term =zero

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Smruti Ranjan Sahoo  (8 years ago)

t3 + t5 = t6+t11+t13

t3 = a + 2d
=> a+2d + a +14d = a +5d + a +10d + a + 12d
=> a + 11d = 0
=> 12th term gives 0 .(Ans)

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name  (5 years ago)

Given==> t3 + t5 = t6+t11+t13

We know===> t3 = a + 2d
=>( a+2d )+ (a +14d) = (a +5d) +( a +10d) + (a + 12d)
=>2a+16d = 3a+27d
=> a + 11d = 0
=> 12th term gives 0
Therefore option "C" is the answer

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