A tower has (6) windows on the first floor and (2) more windows on each next floor. How many windows are on the (12)th floor?
Answer and explanation
Correct answer: 28
The numbers of windows form an AP with first term \(a=6\) and common difference \(d=2\). For the 12th floor, \(a_{12}=a+(12-1)d=6+11\times2=28\). Therefore, 28 is correct. Choosing 26 would incorrectly use 10 increases; there are 11 increases from the first floor to the 12th floor. Exam tip: use \(n-1\) in the formula for the \(n\)th term.
Frequently asked questions
What is the correct answer to this question?
28
Why is this the correct answer?
The numbers of windows form an AP with first term \(a=6\) and common difference \(d=2\). For the 12th floor, \(a_{12}=a+(12-1)d=6+11\times2=28\). Therefore, 28 is correct. Choosing 26 would incorrectly use 10 increases; there are 11 increases from the first floor to the 12th floor. Exam tip: use \(n-1\) in the formula for the \(n\)th term.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Arithmetic Progressions (AP). Topic: Word problems based on APs.
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