Question

The number obtained by adding 12 to a natural number is 160 times of the multiplicative inverse of that natural number. Find the number. 

(1) 20 

(2) 16 

(3) 12 

(4) 8

Answer 1

Correct option is (1) 20

x + 12 = 160 x 1/x

⇒ x² + 12x = 160

⇒ x² + 12x - 160 = 0

⇒ x² + 20x - 8x - 160 = 0

⇒ x (x + 20) - 8 (x + 20) = 0

x = 8, x = -20

x = 8

∴ Number = 8 + 12 = 20