1
Question
Find the nth term of an A.P. whose 6th and 8th terms are 12 and 22 respectively.
Find the nth term of an A.P. whose 6th and 8th terms are 12 and 22 respectively.
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Solution
The correct option is C 5n - 18
Shotcut Approach:
Check the options.
5n - 18 ⇒5×6−18=12
and 5×8−18=22
Conventional Approach:
T6=a+5d=12......(1)T8=a+7d=22⇒2d=10 or d=5∴a+25=12[from eq.(1)]
⇒a=−13∴Tn=−13+(n−1)5⇒Tn=5n−18
Shotcut Approach:
Check the options.
5n - 18 ⇒5×6−18=12
and 5×8−18=22
Conventional Approach:
T6=a+5d=12......(1)T8=a+7d=22⇒2d=10 or d=5∴a+25=12[from eq.(1)]
⇒a=−13∴Tn=−13+(n−1)5⇒Tn=5n−18
Suggest Corrections
12
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