110.
All the 500s start with a 5 so that is 100 numbers that start (or end) with a 5.
Of the 400s, only those which ends with a 5 will do which are 405, 451, ..., 495. ie once for each possible tens digit; the tens digit can be one of 0, 1, ..., 9, ie one of 10 values, so there are a further 10 numbers that (start or) end with a 5.
making 100 + 10 = 110 numbers in all.
I would just call it a "400-digit number".
59
30
All of the four-digit multiples of 400 end in 00.
30 of them.
110...... 500 to 599=100 405.415 till 495
400 of them.
I would just call it a "400-digit number".
59
30
5*5*4*4 = 400
All of the four-digit multiples of 400 end in 00.
It is the first or leftmost digit: 4.
138 of them.
30 of them.
If you write all of the counting numbers from 200 to 400,you will write the digit ' 5 ' forty times.
400/4= 100 and 800/4=200