Verified answer

EXPLANATION.

Nth term of an Ap

=> An = a + ( n - 1 ) d

To find the 18th term.

7 times the 7th term of an Ap us equal to

11 times the 11th term of an Ap

=> 7 ( a + 6d ) = 11 ( a + 10d )

=> 7a + 42d = 11a + 110d

=> -4a = 110d - 42d

=> -4a = 68d

=> a = -17d

18th term of an Ap

=> a + 17d

=> -17d + 17d

=> 0

Therefore,

option [ D ] is correct.

Some related formula.

1) = Nth term of an Ap

=> An = a + ( n - 1 ) d

2) = sum of Nth term of an Ap

=> Sn = n/2 ( 2a + ( n - 1 ) d)

Given:-

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if 7 times seventh term of an A.P is equal to 11 times eleventh term.

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To Find:-

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Then it's eighteenth term will be

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1. 7

2. 11

3. 18

4. 0

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STEP BY STEP EXPLANATION:-

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