New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    In each of the following questions a number series is given.  One term of the series is denoted by x. You have to calculate the value of x  and by using the value of x,  you have  to replace the question mark (?) in the following questions :

    If  2.5   3.5           x         30    

         124       625 Then,  x² - 1 - 2x = ?
    A 80 Correct Answer Incorrect Answer
    B 75 Correct Answer Incorrect Answer
    C 62 Correct Answer Incorrect Answer
    D 92 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    2.5 ×  1 + 1 = 3.5 3.5 ×  2 + 2 = 9 9 ×  3 + 3 = 30 30 × 4 + 4 = 124 124 × 5 + 5 = 625 Hence, x = 9 Hence, 9²-1 - 2× 9  = 81 - 1 - 18 = 62

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