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If a geometric progression has (a_1=7) and (r=5) what is (a_3)?
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Answer and explanation
Correct answer: 175
The nth term of a geometric progression is \(a_n=a_1r^{n-1}\). Therefore, \(a_3=7\times5^{3-1}=7\times25=175\). The value 35 is only the second term, since \(a_2=7\times5\). Exam tip: for the third term, use \(r^2\) in the general-term formula.
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What is the correct answer to this question?
175
Why is this the correct answer?
The nth term of a geometric progression is \(a_n=a_1r^{n-1}\). Therefore, \(a_3=7\times5^{3-1}=7\times25=175\). The value 35 is only the second term, since \(a_2=7\times5\). Exam tip: for the third term, use \(r^2\) in the general-term formula.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Geometric Progression.
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