Let n is number of pages. i is the page which was  removed.

1+...+n -i =3030

3030+i=(n+1) * n :2 

2000=2^4 * 5^3 = 2*2*2*2*125 = 5*5*5*2*8

=> min (a+b+c+d)=5+5+5+2+8=25

There are 25 , 50 , 75 , 100.

Sum of digits 2+5+5+7+5+1=25

1 way or only way

10=1+2+3+4 (1 way)     => 15=1+2+3+4+5

Pigeonhole principle ?

less than 15 minutes at 48 km / h

=>less than 30 minutes at 96 km / h

85!=1 x 2 x 3 x ... x 84 x 85

42=2 x 3 x7

85! has 42 numbers \(⋮\)2

______28 _______ \(⋮\)3

______12________\(⋮\)7

=> k=12.