What is the (20)th term of the sequence (-2,3,8,13,\ldots)?
Answer and explanation
Correct answer: 93
This is an arithmetic progression because the difference between consecutive terms is 5. Here, \(a=-2\), \(d=5\), and \(n=20\). Therefore, \(a_{20}=a+(n-1)d=-2+(20-1)\times5=-2+95=93\). Hence, 93 is correct. Getting 98 usually results from miscounting the terms or using an incorrect value in place of \(n-1\). Exam tip: for an arithmetic progression, always use \(a_n=a+(n-1)d\).
Frequently asked questions
What is the correct answer to this question?
93
Why is this the correct answer?
This is an arithmetic progression because the difference between consecutive terms is 5. Here, \(a=-2\), \(d=5\), and \(n=20\). Therefore, \(a_{20}=a+(n-1)d=-2+(20-1)\times5=-2+95=93\). Hence, 93 is correct. Getting 98 usually results from miscounting the terms or using an incorrect value in place of \(n-1\). Exam tip: for an arithmetic progression, always use \(a_n=a+(n-1)d\).
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Explicit or general rule.
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