If \(a_n=2\cdot5^{n-1}\) what is the value of \(a_4\)?
Answer and explanation
Correct answer: 250
Given \(a_n=2\cdot5^{n-1}\), substitute \(n=4\): \(a_4=2\cdot5^{4-1}=2\cdot5^3=2\cdot125=250\). Hence, option C is correct. Option D can result from an error in multiplying after evaluating \(5^3\). Exam tip: substitute the term number first, and then evaluate the exponent carefully.
Frequently asked questions
What is the correct answer to this question?
250
Why is this the correct answer?
Given \(a_n=2\cdot5^{n-1}\), substitute \(n=4\): \(a_4=2\cdot5^{4-1}=2\cdot5^3=2\cdot125=250\). Hence, option C is correct. Option D can result from an error in multiplying after evaluating \(5^3\). Exam tip: substitute the term number first, and then evaluate the exponent carefully.
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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