Q6 of 46 Page 1

Which term of the A.P. 4, 7, 10, ... is 64 ?

Given: AP is 4, 7, 10, …


To find : n


Proof: Here, a = 4, d = 7 – 4 = 3 and an = 64


We have,


an = a + (n – 1)d


⇒ 64 = 4 + (n – 1) × (3)


⇒ 64 – 4 = 3(n – 1)


⇒ 60 = 3(n – 1)



⇒ 20 = n – 1


⇒ 20 + 1 = n


⇒ n = 21


Therefore, the 21st term of the given AP is 64.


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