Q.

Find the median of the first 15 odd numbers.


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a

12

b

13

c

14

d

15 

answer is D.

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Detailed Solution


In simple terms, we can say that the median is the middle term. For a small sequence, we can simply count the middle term and write the answer. But for larger sequences, we use the formula for the middle term in terms of the number of terms of the sequence.
The formula is given by
 median=n+12th term   if n is odd. And
 median=n2th term +n2+1th term2    if n is even.
The term can be found by either counting it, or by using the formulae of the nth term of sequence.
Now, in the question, it is given that we have the sequence of the first 15 odd numbers. It can be written as
 S={1,3,5,7,...,15}
When we observe, we can say that every term of this sequence is represented by the formula,
 tn=2n−1
where n is the number of term
since, there are 15 terms and 15 is an odd number. The formula we use to find the median will be
 median=n+12th term
Now, n+12th term is tn+12  . i.e.
 tn+12=2n+12-1
Here n=15
Thus the median will be
t15+12=215+12-1
 t8=16-1
 ⇒median= t8 = 15
Therefore, the median of the first 15 odd numbers is 15.
So, the correct answer is “15”.
 
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