Question of The Day03-10-2019

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 ) 35

Explanation :

For arithmetic progression, any nth term is identified as

an=a+(n-1)*d

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

a15=-14+14*(7/2)=35

Hence, (A) is the correct answer.

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