Ok so first we need to determine what is the greatest possible whole number remainder if we divide by 41. If we divide some number x by some other number y, or x:y, we can get a number and a remainder. The remainder we can divide again if its greater than or equal to y and we repeat the procedure until we get a remainder that we can't divide further because it is smaller than y. So when we divide by 41 the greatest possible whole number divider is 40 because we can't divide 41 with 40 and get a whole number.
The greatest possible whole number remainder if you divide a number by 41 is 40.
It can't be 41 because, if the remainder is 41, the remainder can divided by 41
Hope this helped.