What is the value of (a) for (2x+ay=5) and (6x+9y=15) to have infinitely many solutions?
Answer and explanation
Correct answer: 3
For two linear equations to have infinitely many solutions, the condition is \(\frac{a_1}{a_2}=\frac{b_1}{b_2}=\frac{c_1}{c_2}\). Here, \(\frac{2}{6}=\frac{5}{15}=\frac{1}{3}\). Therefore, \(\frac{a}{9}=\frac{1}{3}\), giving \(a=3\). Hence, option B is correct. Exam tip: infinitely many solutions require all three coefficient-to-constant ratios to be equal; equality of only two ratios is not sufficient.
Frequently asked questions
What is the correct answer to this question?
3
Why is this the correct answer?
For two linear equations to have infinitely many solutions, the condition is \(\frac{a_1}{a_2}=\frac{b_1}{b_2}=\frac{c_1}{c_2}\). Here, \(\frac{2}{6}=\frac{5}{15}=\frac{1}{3}\). Therefore, \(\frac{a}{9}=\frac{1}{3}\), giving \(a=3\). Hence, option B is correct. Exam tip: infinitely many solutions require all three coefficient-to-constant ratios to be equal; equality of only two ratios is not sufficient.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Pair of Linear Equations in Two Variables. Topic: Conditions for solvability.
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