Mathematics
Show that the progression 13, 20, 27, 34, …….. is an A.P. Write down its :
(i) first term
(ii) common difference
(iii) 20th term.
AP
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Answer
Since, 20 - 13 = 7, 27 - 20 = 7, and 34 - 27 = 7.
Hence, the series is an A.P. with common difference = 7.
We know that,
nth term of an A.P. is given by,
⇒ an = a + (n - 1)d, where a is the first term.
⇒ a20 = 13 + (20 - 1)7
= 13 + (19) × 7
= 13 + 133
= 146.
Hence, a = 13, d = 7 and a20 = 146.
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