If (M(t)=80+7t) and (N(t)=170-5t), when will (M(t)) be (18) more than (N(t))?
Answer and explanation
Correct answer: \(t=9\)
“18 more” means \(M(t)=N(t)+18\). Thus, \(80+7t=170-5t+18\), or \(80+7t=188-5t\). Therefore, \(12t=108\), giving \(t=9\). Option \(t=10\) may seem close, but it gives a difference of \(30\), not \(18\). Exam tip: In “more than” questions, write the larger quantity as the smaller quantity plus the stated difference.
Frequently asked questions
What is the correct answer to this question?
\(t=9\)
Why is this the correct answer?
“18 more” means \(M(t)=N(t)+18\). Thus, \(80+7t=170-5t+18\), or \(80+7t=188-5t\). Therefore, \(12t=108\), giving \(t=9\). Option \(t=10\) may seem close, but it gives a difference of \(30\), not \(18\). Exam tip: In “more than” questions, write the larger quantity as the smaller quantity plus the stated difference.
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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