Permutation Combination Question 7
Question 7 - 29 January - Shift 1
If all the six digit numbers $x_1 x_2 x_3 x_4 x_5 x_6$ with $0<x_1<x_2<x_3<x_4<x_5<x_6$ are arranged in the increasing order, then the sum of the digits in the $72^{\text{th }}$ number is ______
Show Answer
Answer: 32
Solution:
Formula: Permutation under restrictions
$245678 \to 72^{\text{th }}$ word
$2+4+5+6+7+8=32$
