What is the 25th term of the sequence (7, 13, 19, 25, \ldots)?
Answer and explanation
Correct answer: 151
This is an arithmetic sequence because consecutive terms differ by the constant amount 6. Its nth-term formula is a_n=a_1+(n-1)d=7+(n-1)6, which simplifies to a_n=6n+1. For the 25th term, substitute n=25: a_25=6(25)+1=150+1=151. Therefore option C is correct. Option A corresponds to using an incorrect difference or index adjustment, option B is one less than the correct value, and option D is one term-step too high. The important principle is to use the same common difference for every step and to count 24 differences from the first term to the 25th term, not 25 differences.
Frequently asked questions
What is the correct answer to this question?
151
Why is this the correct answer?
This is an arithmetic sequence because consecutive terms differ by the constant amount 6. Its nth-term formula is a_n=a_1+(n-1)d=7+(n-1)6, which simplifies to a_n=6n+1. For the 25th term, substitute n=25: a_25=6(25)+1=150+1=151. Therefore option C is correct. Option A corresponds to using an incorrect difference or index adjustment, option B is one less than the correct value, and option D is one term-step too high. The important principle is to use the same common difference for every step and to count 24 differences from the first term to the 25th term, not 25 differences.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: nth term.
Student feedback
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
