If (a_{n+1}-a_n=11) and (a_7=58), what is (a_{17})?
Answer and explanation
Correct answer: 168
Since \(a_{n+1}-a_n=11\), the common difference is \(d=11\). There are 10 term-steps from \(a_7\) to \(a_{17}\), so \(a_{17}=a_7+(17-7)d=58+10\times11=168\). Hence, option D is correct. A value such as 166 results from an error in counting the term difference or multiplying. Exam tip: use \(a_n=a_m+(n-m)d\) when one term of an AP is known.
Frequently asked questions
What is the correct answer to this question?
168
Why is this the correct answer?
Since \(a_{n+1}-a_n=11\), the common difference is \(d=11\). There are 10 term-steps from \(a_7\) to \(a_{17}\), so \(a_{17}=a_7+(17-7)d=58+10\times11=168\). Hence, option D is correct. A value such as 166 results from an error in counting the term difference or multiplying. Exam tip: use \(a_n=a_m+(n-m)d\) when one term of an AP is known.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Arithmetic Progressions (AP). Topic: Finding the $n$th term of an AP.
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