Riddle answer : As many as you like -- (100-10) will always equal 90.
However, if it isn't a riddle, the answer would be 10 to reach 0. You could continue to subtract 10 an infinite number of times, yielding an increasing negative value.
Ten
10 times
5
Once! After you have subtracted it once, you are subtracting 100 from 1900, and then 100 from 1800 and on and on
10
As many times as you feel like it before you get bored and stop. After 10 times, you will be left with zero, and you'll begin going into negative numbers. Bu that should be no problem for you. I thought that it would be only once because then you are subtracting from the number 90 not 100.
10 times.
10 times
100 times 3 divided by 10 plus 25 subtract 5 EQUALS 50 unless there are parentheses...
10 times.. because.. 100 * 10 = 1000
9 times with a remainder of 10
ten times
100 is ten times more than 10