A newspaper seller sells (110) newspapers on the first day and (15) more newspapers each next day. On which day will (320) newspapers be sold?
Answer and explanation
Correct answer: 15
This is an arithmetic progression with first term 110 and common difference 15. The sales on the nth day are \(a_n=110+(n-1)\times15\). Putting \(a_n=320\), we get \(110+15(n-1)=320\), so \(15(n-1)=210\), \(n-1=14\), and \(n=15\). Therefore, 320 newspapers will be sold on the 15th day. The nearby option 13 is incorrect because sales on that day would be \(110+12\times15=290\). Exam tip: In day-number AP questions, remember to use \(n-1\).
Frequently asked questions
What is the correct answer to this question?
15
Why is this the correct answer?
This is an arithmetic progression with first term 110 and common difference 15. The sales on the nth day are \(a_n=110+(n-1)\times15\). Putting \(a_n=320\), we get \(110+15(n-1)=320\), so \(15(n-1)=210\), \(n-1=14\), and \(n=15\). Therefore, 320 newspapers will be sold on the 15th day. The nearby option 13 is incorrect because sales on that day would be \(110+12\times15=290\). Exam tip: In day-number AP questions, remember to use \(n-1\).
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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