# 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