Assuming you are asking how many times the digit 1 appears when writing the numbers 400 to 500:
It appears in the tens place once (41x where x is any digit 0-9) so there will be 10 occurrences of it here.
It appears in the ones place for every digit in the tens place (4x1) so there will be 10 occurrences of it here.
However, the number 411 has been counted twice, once as 41x and again as 4x1.
Thus the digit 1 will be written 10 + 10 - 1 = 19 times.
There are 200000 lots of 1/400 in 500.
400 of them.
400/500 = 400 ÷ 500 = 0.8
200 + 300 200 + 200 + 100
500
8000 ÷ 20 = 400
400
The hundreds, on either side of 449 are 400 and 500. 449 is 49 away from 400, and 51 away from 500. So the nearest hundred is 400.
400
It is closer to 500.
400 + 500 = 900
It is 500.
400 multiplied by 500 is 200,000.