The 9th term and the 21st term of an AP are 75 and 183 respectively.find 81th term of the AP
Answers
Answered by
31
an aps generalised form is,
an=a+(n-1)d.
so,for the 9th term,
75=a+8d
(1)st equation
so,for the 21st trm,
183=a+20d
(2)nd equation
equate both equations
so,
12d=108
d=9
put,d=9 in eq. (1)
75=a+72
a=3
now,we have to find the 81st term
an=3+80×9
81st=3+720
81st term =723
an=a+(n-1)d.
so,for the 9th term,
75=a+8d
(1)st equation
so,for the 21st trm,
183=a+20d
(2)nd equation
equate both equations
so,
12d=108
d=9
put,d=9 in eq. (1)
75=a+72
a=3
now,we have to find the 81st term
an=3+80×9
81st=3+720
81st term =723
Answered by
20
723 is the correct answer
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