Question

Counting question

Answer 1

\(\large \color{black}{\begin{align}
& \normalsize \text{How many numbers lying between 100 and 1000 }\hspace{.33em}\\~\\
& \normalsize \text{can be formed with the digits 0, 1, 2, 3, 4, 5,}\hspace{.33em}\\~\\
& \normalsize \text{ if the repetition of the digits is not allowed?}\hspace{.33em}\\~\\

\end{align}}\)

Answer 2

I'm in counting principles

Answer 3

not good *

Answer 4

lol what u want to say

Answer 5

Let's just take three-digit numbers (1000 won't be counted anyway).

_ _ _

Whenever repetition is not allowed, we reduce the number of choices by 1 for each subsequent blank.

The leftmost blank allows 1, 2, 3, 4, 5 so 5 numbers.
The second blank allows 4 numbers but zero is also included, so 5 numbers.
The last blank allows 4 numbers.

The total number is 5 * 5 * 4 = 100.