If (C(x)=140-8x) and (D(x)=100-3x), when will both be equal?
Answer and explanation
Correct answer: \(x=8\)
For the two values to be equal, set \(140-8x=100-3x\). This gives \(40=5x\), so \(x=8\). On checking, \(C(8)=140-64=76\) and \(D(8)=100-24=76\). At \(x=6\), their values are different, so it is not correct. Exam tip: to find where two linear expressions are equal, equate them first and solve for \(x\).
Frequently asked questions
What is the correct answer to this question?
\(x=8\)
Why is this the correct answer?
For the two values to be equal, set \(140-8x=100-3x\). This gives \(40=5x\), so \(x=8\). On checking, \(C(8)=140-64=76\) and \(D(8)=100-24=76\). At \(x=6\), their values are different, so it is not correct. Exam tip: to find where two linear expressions are equal, equate them first and solve for \(x\).
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Introduction to Polynomials. Topic: Linear growth and decay.
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