 # Linear Equations ( 6 to 10 )

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Linear Equations ( 6 to 10 ):

# APTITUDE QUESTIONS (LINEAR EQUATIONS):

6. If a(x – a2) – b(x – b2) = 0, then x is equal to

A) (-a+b)(a2+ ab+b2)/(a+b)

B)    a3+ b3/(a-b)

C)    a3– b3/(a+b)

D)    a2 + ab + b2

E)    None of these

Explanation:
ax – a3 – bx + b3 = 0
x = (a3– b3)/(a-b) = a2 + ab + b2

7. If 7x: 63 = 1:9, then x is equal to

A)    3

B)    2

C)    1

D)    -1

E) None of these

Explanation:
7x/63= 1/9 => x = 1

8. If 5 added to twice of a number it becomes 6, then the number is

A)    0.5

B)    5

C)    0.25

D)    0.05

E)    None of these

Explanation:
∵ 2x + 5 = 6
=> 2x = 1
=> x = 0.5

9. The sum of the two numbers is 11 and their product is 30, then the numbers are

A)    8, 3

B)    9, 2

C)    7, 4

D)    5, 6

E)    None of these

Explanation:
Let numbers be x and 11 – x
=> x(11 – x) = 30

=> (x – 5) (x – 6) = 0

=> x = 5, 6

10. If one number is thrice the other and their sum is 20, then the numbers are

A)    5, 15

B)    4, 12

C)    3, 9

D)    6, 18

E)    None of these

Explanation:
x + 3x = 20

=> x = 5