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STD 11 - 6. permutation and combination — JEE STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceJEESTD 11 - 6. permutation and combination4 Marks
MCQ
$^{47}{C_4} + \mathop \sum \limits_{r = 1}^5 {}^{52 - r}{C_3} = $
  • A
    $^{47}{C_6}$
  • B
    $^{52}{C_5}$
  • ✓
    $^{52}{C_4}$
  • D
    None of these
✓

Answer

Correct option: C.
$^{52}{C_4}$
c
(c) $^{47}{C_4} + \sum\limits_{r = 1}^5 {^{52 - r}{C_3}} { = ^{51}}{C_3}{ + ^{50}}{C_3}{ + ^{49}}{C_3}{ + ^{48}}{C_3}{ + ^{47}}{C_3}{ + ^{47}}{C_4}$

${ = ^{51}}{C_3}{ + ^{50}}{C_3}{ + ^{49}}{C_3}{ + ^{48}}{C_3}{ + ^{48}}{C_4}$

${ = ^{51}}{C_3}{ + ^{50}}{C_3}{ + ^{49}}{C_3}{ + ^{49}}{C_4}$

${ = ^{51}}{C_3}{ + ^{50}}{C_3}{ + ^{50}}{C_4}{ + ^{51}}{C_3}{ + ^{51}}{C_4}$

$={^{52}}{C_4}$.

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