Question

Number of ways of selection of $4$ letters of the word PERFECT is____.

Answer 1

Answer: 25

$7$ letters
$P\to 1$
$E\to 2$
$R\to 1$
$F\to 1$
$C\to 1$
$T\to 1$
$2$ alike $+2$ diff. $=1\times {}^5{C}_2=10$
All $4$ different $={}^6{C}_4=15$
Total $=15+10=25$