Mathematics
Find the nth term of the A.P. 5, 11, 17, 23,……. Using it, find its
(i) 11th term
(ii) 21st term.
AP
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Answer
Given,
a = 5
d = 11 - 5 = 6
nth term of an A.P. is given by,
an = a + (n - 1)d
an = 5 + (n - 1)6
= 5 + 6n - 6
= 6n - 1.
(i) 11th term:
⇒ a11 = 5 + (11 - 1)6
= 5 + 10(6)
= 5 + 60
= 65.
(ii) 21st term
⇒ a21 = 5 + (21 - 1)6
= 5 + (20)6
= 5 + 120
= 125.
Hence, nth term = 6n - 1, 11th term = 65 and 21st term = 125.
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