bmwhype2 wrote:

How many times will the digit 7 be written when listing from 1 to 1000?

110

111

271

300

304

D,

we have 3 options for numbers between 1 and 1000

one digit: 0, 1,2,3......9.

two digits: 10,11........99

three digits: 100.........999

1000 does not have 7, so no need to count it.

one digit: only 1 number

two digits: 1*10+9*1=19 numbers

there are 1*10 two digit numbers that have 7 as first digit and any other (from 0 to 9 digit) as second digit. And there are 9*1 two digit numbers that have any other (from 1 to 9 digit) as first digit and 7 as second digit.

Zero can not be first intenger.

three digits: 1*10*10+9*1*10+9*10*1=280 numbers

same logic as for two digit numbers.

The total number of 7`s that will be written is
1+19+280=300.

I got this question wrong cuz i mis read the question....i counted numbers from 1-100 that have digit 7, (in this case you would have to minus repeatitions ) but the questions says "many times will the digit 7 be written", thus no need to minus repeatition.