JEE MainMathematicsSequences and SeriesMCQ+4 / −1
Let , , , ......... , be in A.P. such that and . , then m is equal to
- A33
- B66
- C68
- D34
View written solutionFree
Correct answer: D
- Write the A.P. in standard form
Let the A.P. be where and is the common difference.
- Use the first condition
We are given
Now, So the terms are: This is an A.P. with 13 terms.
Hence,
Now, So,
- Use the second condition
Given
Now, So,
- Solve for and
Subtract (1) from (2):
Put into (1):
Thus the A.P. is
- Compute
Since ,
Therefore,
This is
Using we get
So,
Given so
- Check options
The value is So the correct option is D.
- Comparison with stored answer
Stored correct answer: D
Derived answer: D
They agree.
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