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

Answer: Option B

Solution(By Examveda Team)

Let the number be x
Then,
$$\eqalign{ & \Leftrightarrow 3{x^2} - 4x = x + 50 \cr & \Leftrightarrow 3{x^2} - 5x - 50 = 0 \cr & \Leftrightarrow \left( {3x + 10} \right)\left( {x - 5} \right) = 0 \cr & \Leftrightarrow x = 5 \cr} $$