If the 7th term of an arithmetic progression is 7 and 11th term of the same arithmetic progression is 21 then, what will be the 15th term of the progression?
Correct Answer : a ) 35Explanation :
For arithmetic progression, any nth term is identified as
Where, a = 1st term of the progression
an = nth term of the progression
d = is the common difference
According to the question,
7th term of the arithmetic progression is 7
So, a7 = a + 6d = 7…….. (I)
11th term of the arithmetic progression is 21
So, a11 = a + 10d = 21……… (II)
Solving equation (I) and (II) for a and d, we get
a = – 14 and d=7/2
Thus, 15th term of the progression will be
a15 = a + 14d
Hence, (A) is the correct answer.
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