JEE Mains · Maths · STD 11 - 8. sequence and series
Let the sum of the first three terms of an \(A. P,\) be \(39\) and the sum of its last four terms be \(178.\) If the first term of this \(A.P.\) is \(10,\) then the median of the \(A.P.\) is
- A \(28\)
- B \(26.5\)
- C \(29.5\)
- D \(31\)
Answer & Solution
Correct Answer
(C) \(29.5\)
Step-by-step Solution
Detailed explanation
\({a_1} + {a_2} + {a_3} = 39\) \( \Rightarrow {a_1} + \left( {{a_1} + d} \right) + \left( {{a_1} + 2d} \right) = 39\) \( \Rightarrow 3{a_1} + 3d = 39\,\,\,\,\,\,\,\,\left[ {{a_1} = 10} \right]\) \( \Rightarrow d = 3\) Sum of last four term \(=178\) Their mean…
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