A school bus travels (15) km on the first day and (5) km more each next day. How far will the bus travel on the (8)th day?
Answer and explanation
Correct answer: 50 km
The distances travelled each day form an AP with first term \(a=15\) km and common difference \(d=5\) km. The \(n\)th term is \(a_n=a+(n-1)d\). Therefore, \(a_8=15+(8-1)\times5=15+35=50\) km. Hence, 50 km is correct. Choosing 55 km would give the 9th term, not the 8th term. Exam tip: Use \(n-1\), not \(n\), in the nth-term formula.
Frequently asked questions
What is the correct answer to this question?
50 km
Why is this the correct answer?
The distances travelled each day form an AP with first term \(a=15\) km and common difference \(d=5\) km. The \(n\)th term is \(a_n=a+(n-1)d\). Therefore, \(a_8=15+(8-1)\times5=15+35=50\) km. Hence, 50 km is correct. Choosing 55 km would give the 9th term, not the 8th term. Exam tip: Use \(n-1\), not \(n\), in the nth-term formula.
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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