Quantitative Ability (Part 9 of 9)

Let S denote the infinite sum 2 + 5x + 9 × 2 + 14 × 3 + 20 × 4 + ____, where x < 1 and the coefficient of xn1 is 1/2n (n + 3) (n = 1, 2, … ), Then S equals

2 − x/(1 − x) 3

2 − x/(1 + x) 3

2 + x/(1 − x) 3

2 + x/(1 + x) 3
Answer: a


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 + v5

1 − v5

v7

2v7
Answer: a


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 (xk) 2 + y2 = 1

2

0

v2

v2
Answer: c


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.

(zx)/(yx)

(xz)/(yz)

(yx)/(zy)

(yz)/(xz)
Answer: a
