If (M(t)=62+5t) and (N(t)=142-5t), when will (M(t)) be (20) more than (N(t))?
Answer and explanation
Correct answer: \(t=10\)
“20 more” means \(M(t)=N(t)+20\). Thus, \(62+5t=142-5t+20\), or \(62+5t=162-5t\). This gives \(10t=100\), so \(t=10\). At \(t=8\), the difference is 0, so it is a close but incorrect option. Exam tip: for “more than” questions, equate the larger quantity to the smaller quantity plus the stated difference.
Frequently asked questions
What is the correct answer to this question?
\(t=10\)
Why is this the correct answer?
“20 more” means \(M(t)=N(t)+20\). Thus, \(62+5t=142-5t+20\), or \(62+5t=162-5t\). This gives \(10t=100\), so \(t=10\). At \(t=8\), the difference is 0, so it is a close but incorrect option. Exam tip: for “more than” questions, equate the larger quantity to 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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