Question
$^{47}{C_4} + \mathop \sum \limits_{r = 1}^5 {}^{52 - r}{C_3} = $
${ = ^{51}}{C_3}{ + ^{50}}{C_3}{ + ^{49}}{C_3}{ + ^{48}}{C_3}{ + ^{48}}{C_4}$
${ = ^{51}}{C_3}{ + ^{50}}{C_3}{ + ^{49}}{C_3}{ + ^{49}}{C_4}$
${ = ^{51}}{C_3}{ + ^{50}}{C_3}{ + ^{50}}{C_4}{ + ^{51}}{C_3}{ + ^{51}}{C_4}$
$={^{52}}{C_4}$.
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