Question
find the number of two digit natural numbers such that the tens digit is greater than the units digit.
Answers
Steve
20 21
30 31 32
...
90 91 92 ... 98
2+3+...+9
= 44
30 31 32
...
90 91 92 ... 98
2+3+...+9
= 44
Gheena
Write in extension the set S of the two digit natural integers whose tens digit is twice that of the unit digit