There aren't going to be any 7's in the hundreds digit, so first we look at how many there will be in the ones digit.
Since there will be a 7 for every 10 numbers, and there are 501 numbers between 100 and 600 inclusive), we'll have floor(501 / 10) = 50 sevens in the ones digit.
For the tens digit, we'll encounter 10 sevens for every 100, from 70 to 79, and so we have floor(501 / 100) = 5 times we'll have 70 - 79 so that's 5 * 10 = 50 sevens in the tens digit.
However, we don't want to know how many sevens there are, we want to exclude overlaps. Thus we subtract every instance of 77 we see (overlap!), and we have floor(501 / 100) = 5 overlaps.
50 + 50 - 5 = 95, so a total of 95 numbers will have the digit 7 at least once.
176
There are 6484 digits BETWEEN the two given numbers.
There is only one number and that is 123456.
223
The number is: 36725918 In descending order that is: 98765321 The pairs of numbers that have as many digits between them in both are: 3,9 5,8 6,7 So there are three pairs.
176
I think its more then 20
19 do.
Only one. 123456.
Twenty of them from 9 to 99
There are 6484 digits BETWEEN the two given numbers.
There is only one number and that is 123456.
223
123
The number is: 36725918 In descending order that is: 98765321 The pairs of numbers that have as many digits between them in both are: 3,9 5,8 6,7 So there are three pairs.
The sum of the number of digits in all the numbers between 31 and 400 inclusive is 1041.
Numbers formed should be of at least 3 digits means they may be of 3 digits, 4 digits, 5 digits or 6 digits. There are 6 choices for digit in the units place. There are 5 and 4 choices for digits in ten and hundred’s place respectively. So, total number of ways by which 3 digits numbers can be formed = 6.5.4 = 120 Similarly, the total no.of ways by which 4 digits numbers can be formed = 6.5.4.3 = 360. the total no. of ways by which 5 digits numbers can be formed = 6.5.4.3.2 = 720. The total no.of ways by which 4 digits numbers can be formed = 6.5.4.3.2.1 = 720. So, total no.of ways by which the numbers of at least 3 digits can be formed = 120 + 360 + 720 + 720 = 1920.