If (a=2), (d=5), what will be the (15)th term of the AP?
Answer and explanation
Correct answer: 72
The formula for the nth term of an AP is \(a_n=a+(n-1)d\). Therefore, \(a_{15}=2+(15-1)\times5=2+70=72\). Hence, 72 is correct. The option 75 results from incorrectly adding \(15\times5\); only 14 common differences are added to reach the 15th term. Exam tip: always use \((n-1)\), not \(n\), in the nth-term formula.
Frequently asked questions
What is the correct answer to this question?
72
Why is this the correct answer?
The formula for the nth term of an AP is \(a_n=a+(n-1)d\). Therefore, \(a_{15}=2+(15-1)\times5=2+70=72\). Hence, 72 is correct. The option 75 results from incorrectly adding \(15\times5\); only 14 common differences are added to reach the 15th term. Exam tip: always use \((n-1)\), not \(n\), in the nth-term formula.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Arithmetic Progressions (AP). Topic: Finding the $n$th term of an AP.
