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Arithmetic Progressions — Maths STD 10 — Question

CBSE BoardEnglish MediumSTD 10MathsArithmetic Progressions1 Mark
MCQ
In $a_n \ \ A.P$. if $d = -4, n = 7$ and $a_n= 4,$ then $'a\ '$ is :
  • A
    $20$
  • B
    $6$
  • ✓
    $28$
  • D
    $7$
✓

Answer

Correct option: C.
$28$
Given : $d = -4, n = 7$ and $a_n= 4$
$\therefore a_n= a + (n - 1)d$
$\Rightarrow 4 = a + (7 - 1) \times (-4)$
$\Rightarrow 4 = a + 6 \times -4$
$\Rightarrow 4 = a - 24$
$\Rightarrow a = 28$

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