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8. Sequences and Series
easy
The four arithmetic means between $3$ and $23$ are
A
$5, 9, 11, 13$
B
$7, 11, 15, 19$
C
$5, 11, 15, 22$
D
$7, 15, 19, 21$
Solution
(b) Let four arithmetic means are ${A_1},{A_2},\;{A_3}$ and ${A_4}$.
So $3,\;{A_1},\;{A_2},\;{A_3},\;{A_4},\;23$
$ \Rightarrow $ ${T_6} = 23 = a + 5d$
$ \Rightarrow $ $d = 4$
Thus ${A_1} = 3 + 4 = 7,\;{A_2} = 7 + 4 = 11,\;$
$A_3 = 11+4 =15 ,\, A_4 = 15+ 4=19$
Standard 11
Mathematics