ABC26GN1670 · Problems on Numbers

Subject: General Aptitude · Chapter: Problems on Numbers · Exam: 2003 · Marks: · Difficulty:

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

Answer (as printed): B

Explanation

Let the number be $x$. Then, $3 x^{2}-4 x=x+50$ $$\begin{aligned} & \Leftrightarrow 3 x^{2}-5 x-50=0 \\ & \Leftrightarrow(3 x+10)(x-5)=0 \\ & \Leftrightarrow x=5 . \end{aligned}$$

Explanation as extracted from the printed page; notation may be imperfect.

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