** 9) Find 4ab when a + b = 15 and a - b = 3**

(A) 18

(B) 24

(C) 234

(D) 216

** 10) Simplify x/15 * 9/y**

(A) 3x/5y

(B) 5x/3y

(C) 9x/15y

(D) x/y

** 11) Simplify a ^{2}/2 ÷ a^{3}/4**

(A) a/2

(B) a

^{6}/8

(C) 4a

^{2}/2a

^{3}

(D) 2/a

** 12) Find the value of a ^{2} - b^{2}/(a-b), when a = 2.9 and b = 9.1**

(A) 122

(B) 92

(C) 12

(D) 25

** 13) What is the value of a and b, If a ^{2} - b^{2} = 36 and a + b = 6**

(A) a = 9, b = 9

(B) a = 6, b = 0

(C) a = 0, b = 6

(D) a = 3, b = 15

** 14) Find the value of xy, when x ^{2} + y^{2} = 58 and x^{2} - y^{2} = 42**

(A) 10

(B) 12

(C) 15

(D) 20

** 15) If x = 235 and y = 117, then x ^{2} - y^{2}/x - y = ?**

(A) 118

(B) 100

(C) 115

(D) 352

** 16) If x ^{2} - y^{2} = 16 and x^{2} + y^{2} = 34, which of the following could be the value of xy?**

I 15

II -15

III 45

(A) only I

(B) only II

(C) I and II only

(D) III only