Quantitative Ability (Part 9 of 9)

  1. Let S denote the infinite sum 2 + 5x + 9 × 2 + 14 × 3 + 20 × 4 + ____, where| x| < 1 and the coefficient of xn-1 is 1/2n (n + 3) (n = 1, 2, … ), Then S equals

    1. 2 − x/(1 − x) 3

    2. 2 − x/(1 + x) 3

    3. 2 + x/(1 − x) 3

    4. 2 + x/(1 + x) 3

    Answer: a

  2. ABCD is a rectangle. The points p and Q lie on AD and AB respectively. If the triangles PAQ, QBC and PCD all have the same areas and BQ = 2, then AQ =

    1. 1 + v5

    2. 1 − v5

    3. v7

    4. 2v7

    Answer: a

  3. For which value of k does the following pair of equations yield a unique solution for x such that the solution is positive? x2 − y2 = 0 (x-k) 2 + y2 = 1

    1. 2

    2. 0

    3. v2

    4. -v2

    Answer: c

  4. In an examination, the average marks obtained by students who passed was x %, while the average of those who failed was y %. The average marks of all students taking the exam was z %. Find in terms of x, y and z, the percentage of students taking the exam who failed.

    1. (z-x)/(y-x)

    2. (x-z)/(y-z)

    3. (y-x)/(z-y)

    4. (y-z)/(x-z)

    Answer: a