EXERCISE 7A (OBJECTIVE TYPE QUESTIONS IN 16 20 SOLUTION )

16.       Twenty times a positive integer is less than its square by 96.waht is the integer?

a)      20

b)      24

c)       30

d)      Cannot be determined.

17.       Thrice the square of a natural number decreased by 4 times the number is equal to 50 more than the number. The number is:

a)      4

b)      5

c)       6

d)      10

18.       The sum of a number and its reciprocal is one-eighth of 34. What is the products of the number and its square root?

a)      8

b)      27

c)       32

d)      None of these

19.       Two – third of a positive number and 25/216 of its reciprocal are equal. The number is:

a)      5/12

b)      12/5

c)       25/144

d)      144/25

20.       Find a positive number which when increased by 17 is equal to 60 times the reciprocal of the number.

a)      3

b)      10

c)       17

d)      20

ANSWERS

16.B

17.B

18.A

19. A

20. A

SOLUTION 

61.       Let the integer be x.

Then, X + X² = 182    X² +X – 182 = 0  ( X + 14 ) ( X – 13) = 0  X = 13.

17.       Let the Integer be x.

Then, X² - 20X = 96     x² - 20X -96 = 0    (X + 4) (X – 24) = 0   X = 24.

18       Let the number be x. then, X + 1/X = 34 /8 x² + 1 / X = 34 / 8     x² + 1 / X = 34 / 8   8X² 

- 34X +8 = 0.

4X² - 17X + 4 = 0     (4 x -1) (X – 4) = 0     X = 4.

Required number = 4 x 4 = 4 x 2 =8.

19.       Let the number be x.

Then, 2/3 X = 25 / 216 x 1/x      x²= 25 / 216 x 3/2 = 25 / 144    x = 25 / 144 = 5/12.

20.       Let the number be x.

Then, x + 17 = 60 / X      x² + 17x – 60 = 0  ( x + 20 ) ( X – 3 ) = 0   x = 3.