   SEARCH HOME Math Central Quandaries & Queries  Question from Kathy, a parent: When dividing a 3 digit number by a 1 digit number, for what divisors can you get a remainder of 8? is the question in my son's math book. After searching this web site, how do you explain an answer so that a ten year old can understand? I somewhat understand the answers given, but am afraid my son might not understand the answer? Help??? Thanks in advance Kathy Kathy,

What you need to explain is that, if for example, you divide a bigger number by 4 then the remainder can only be 0, 1, 2 or 3 because you're taking the big number and dividing into a as many groups of size 4 as possible and seeing what is left over, For example if you divide 100 by 4 you get 25 groups of 4 and 0 left over; with 127 you get 31 groups of 4 and 3 left over, etc.

As to your particular question, if you have 8 left over how big could the groups into which you're dividing the big number into? If, for example, they were groups of 6, the largest amount left over can only be 5, not 8. So, in your case you must have ... ?

Penny     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.