Target Exam

CUET

Subject

General Aptitude Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:

The system of equations $4x + 14y = 18$ and $6x + 21y = 33$ has

Options:

infinite solutions

a unique solution $x = 1, y = 1$

a unique solution $x = 2, y = 1$

no solution

Correct Answer:

no solution

Explanation:

The correct answer is Option (4) → no solution

Step-by-Step Analysis:

To determine the number of solutions for a system of linear equations in the form $a_1x + b_1y = c_1$ and $a_2x + b_2y = c_2$, we compare the ratios of their coefficients:

1. Identify the coefficients:

  • Equation 1: $4x + 14y = 18 ⇒a_1 = 4, b_1 = 14, c_1 = 18$
  • Equation 2: $6x + 21y = 33 ⇒a_2 = 6, b_2 = 21, c_2 = 33$

2. Calculate the ratios:

  • Ratio of x-coefficients: $\frac{a_1}{a_2} = \frac{4}{6} = \frac{\mathbf{2}}{\mathbf{3}}$
  • Ratio of y-coefficients: $\frac{b_1}{b_2} = \frac{14}{21} = \frac{\mathbf{2}}{\mathbf{3}}$
  • Ratio of constants: $\frac{c_1}{c_2} = \frac{18}{33} = \frac{\mathbf{6}}{\mathbf{11}}$

3. Apply the consistency rules:

  • If $\frac{a_1}{a_2} \neq \frac{b_1}{b_2}$, there is a unique solution (lines intersect).
  • If $\frac{a_1}{a_2} = \frac{b_1}{b_2} = \frac{c_1}{c_2}$, there are infinite solutions (lines are coincident).
  • If $\frac{a_1}{a_2} = \frac{b_1}{b_2} \neq \frac{c_1}{c_2}$, there is no solution (lines are parallel).

In this case:

$\frac{2}{3} = \frac{2}{3} \neq \frac{6}{11}$

Since the ratios of the coefficients are equal but not equal to the ratio of the constants, the two lines are parallel and will never intersect. Therefore, the system has no solution