chronolinkz wrote:
how many times will the digit 7 be written when listing the integers from 1 to 1000?
110
111
271
300
304
again any replies i would really appreciate it. this question is giving me this huge headache...lol.
From 1-100 There are 7,17,27,47,57,67,87,97 So multiply this by 10
=90
From 71-79 There are 10 7's (counting 77) = 9*10=90
We are discounting the 700-799 so far.
So total now is 180.
Now counting 700-799. we have 799-700+1=100 #'s. However this doenst cover all of the 7's just yet.
Now consider: 707,717,727,737,747,757,767,787,797 = 9 additional 7's on the end.
Now from 770-779. we have 770,771,772,773,774,775,776,777,778,779. we have 11 7's b/c we have an additional 7 from 777.
so 180+9+11+100=300!
Ans. D.
I don't really see a quick way to solve this. Just gotta know all the possibilities that 7 can show up.
My original answer was actually 301. So come test day i dunno if i would have picked 304 or 300. Not bad to narrow down to 2 answers, but considering i spent bout 3min on the prob. thats no good.