Hi, I just answered m01 and I'm not sure the official answer to q10 is correct.

Q: How many times will the digit 7 be written when listing the integers 1 to 1000?

OA: 300

My calculation: 280

But when I did the calculations, I came up with:

1-10: 7 (1 no.)

11-99: 17,27,37,...97 (9 nos.)

70,71,72,...79 (10 nos.)

100-199: 107,117,127,...197 (10 nos.)

170,171,172,...190 (10 nos.)

So for 100-199, 200-299, 300-399,...900-900 EXCEPT 700-799, there are 8*20 sevens = 160

For 700-799, 100 nos.

So, in total that's 160+100+10+9+1=280.

I think the official answer double-counted the 20 nos. in 100-999, it included 20 nos. in 700 but still added a full 100 nos. in 700-799.

Do correct me if I'm wrong please.