How many times will the digit 7 be written when listing the integers from 1 to 1000?
I took a long long time to solve this and finally threw a hail mary pass. I want to look at different or easy approaches to solve this.
Unfortunately, we don't have any formulaic approach here. Go by the Unit, tens and hundreds approach
so that you don't miss any number.
The number 7 at units place appears once in every 10 digits. So in the first 100 numbers, 7 appears 10 times. We have 10 100s here (100*10= 1000) so we have 7 at units place in 10*10 =100
Next tens place. Again we have 7 appearing 10 times in tens place in the first 100. We have 10 100s(100*10= 1000) here. So 7 at tens place = 10*10 = 100
Next hundreds place. In the first 100 numbers, We have 7 appearing 100 times in hundreds place (from 700 to 799) so that makes another 100.
Add up the three 100s we get 300
"You have to find it. No one else can find it for you." - Bjorn Borg
Check out my GMAT blog - GMAT Tips and Strategies