A newspaper seller sells (140) newspapers on the first day and (25) more newspapers each next day. On which day will (515) newspapers be sold?
Answer and explanation
Correct answer: 16
This is an arithmetic progression with first term \(a=140\) and common difference \(d=25\). Sales on the \(n\)th day are \(a_n=140+(n-1)25\). Setting this equal to 515 gives \(140+(n-1)25=515\), so \((n-1)25=375\), \(n-1=15\), and \(n=16\). Option 15 results from incorrectly treating \(n-1\) as the day number. Exam tip: for day-based AP questions, use \(a_n=a+(n-1)d\).
Frequently asked questions
What is the correct answer to this question?
16
Why is this the correct answer?
This is an arithmetic progression with first term \(a=140\) and common difference \(d=25\). Sales on the \(n\)th day are \(a_n=140+(n-1)25\). Setting this equal to 515 gives \(140+(n-1)25=515\), so \((n-1)25=375\), \(n-1=15\), and \(n=16\). Option 15 results from incorrectly treating \(n-1\) as the day number. Exam tip: for day-based AP questions, use \(a_n=a+(n-1)d\).
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Arithmetic Progressions (AP). Topic: Word problems based on APs.
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