00:01
For this question, we are given these numbers and in part a, we have just write three digits numbers and not repetition.
00:09
So let me just put three dash here.
00:12
So for each of them, so what are the possibilities for the first digit of the number? two, four, so there are six possibilities.
00:21
And if i use one of them, so there is left five possibilities for the next one.
00:26
And for the third one, if i use two of them, so four possibilities.
00:30
So the number of numbers that we can just write three digits non -repeating numbers, which are 120 numbers we can just write.
00:43
And for part b, we have to just find less than the number of numbers, less than 400.
00:50
So let me just put again three dashes.
00:53
If the number is less than 400, what about the hundredth of this number? so there are two possibilities.
01:00
Two or three can come to the hundreds of this number...