15
4,14,24,34,40,41,42,43,44 (is 2),45,46,47,48 and 49
It is used 300 times.
A digit is that which we used to count numbers.
24.
99. Each of the numbers in the list can only be used by itself otherwise you would get a 4-digit (or longer) number.
18
It is used 300 times.
19 times10,11 (is 2),12,13,14,15,16,17,18,19,21,31,41,51,61,71,81 and 91
A digit is that which we used to count numbers.
24.
99. Each of the numbers in the list can only be used by itself otherwise you would get a 4-digit (or longer) number.
6
444
It depends. If the numbers are only used once then it is 24. More precisely it is 4!. (4 factorial which is 4x3x2x1). The same would apply to any number of digits assuming they are used once each. If there is replacement involved (any number used any number of times like 7777 or 6688), then the answer would be 256. Or in other words, the number of possible numbers raised to the power of how many digit positions there are (44). So if the question was how many 5 digit numbers can you make from 1234567?75=16807
1
No, many more times over the millennia that people have used arithmetic.
First 9 pages = 9 digit. That leaves 142 digits. @ 2 digit per page, that is 142/2 = 71 pages with 2-digit numbers. So, 9 pages with 1-digit numbers + 71 pages with 2-digit numbers = 80 pages.
999