If (a_1=20) and (d=-2), what is (a_{12})?
Answer and explanation
Correct answer: \(-2\)
The nth term of an arithmetic progression is \(a_n=a_1+(n-1)d\). Thus, \(a_{12}=20+(12-1)(-2)=20-22=-2\). Therefore, \(-2\) is correct. The value \(0\) would be obtained for the 10th term, not the 12th term. Exam tip: retain the negative sign of \(d\) carefully in a decreasing AP.
Frequently asked questions
What is the correct answer to this question?
\(-2\)
Why is this the correct answer?
The nth term of an arithmetic progression is \(a_n=a_1+(n-1)d\). Thus, \(a_{12}=20+(12-1)(-2)=20-22=-2\). Therefore, \(-2\) is correct. The value \(0\) would be obtained for the 10th term, not the 12th term. Exam tip: retain the negative sign of \(d\) carefully in a decreasing AP.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Arithmetic Progression.
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