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AnilSinghBora
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Find the 20th term from the last term of the A.P. 3, 8, 13, …, 253. Q.17

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The best solution for the class 10th of the important question of arithmetic progressions of ncert of class 10th. How i solve in easy way Find the 20th term from the last term of the A.P. 3, 8, 13, …, 253

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  1. Given A.P. is3, 8, 13, …, 253

    Common difference, d= 5.

    Therefore, we can write the given AP in reverse order as;

    253, 248, 243, …, 13, 8, 5

    Now for the new AP,

    first term, a = 253

    and common difference, d = 248 − 253 = −5

    n = 20

    Therefore, using nth term formula, we get,

    a20 = a+(20−1)d

    a20 = 253+(19)(−5)

    a20 = 253−95

    a = 158

    Therefore, 20th term from the last term of the AP 3, 8, 13, …, 253.is 158.

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