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Deepak Bora
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Choose the correct choice in the following and justify. (i) 30th term of the A.P: 10,7, 4, …, is (A) 97 (B) 77 (C) −77 (D) −87

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This question is from NCERT Book class 10th Ch. no.5 Ex. 5.2 Q. 2 (ii). In this question you have to find the right option and support your answer by giving its solution. Answer the question with brief explanation.

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  1. Solution:

    It is given

    A.P = 10, 7, 4, …

    So, we can find,

    1st term, a = 10

    common diff., d = a2 − a= 7−10 = −3

    For an A.P we use,

    an = a +(n−1)d

    Putting down the value:-

    a30 = 10 + (30−1)(−3)

    a30 = 10 + (29)(−3)

    a30 = 10 − 87 = −77

    So, the correct answer is option C.

     

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