There were three main ways of working this one out.

1. Tom from Tattingstone School, UK used a step-by-step method.
   

   "As I divided I am going to reverse the process by timsing (multiplying) 3.125 by whole numbers under 5 to find the original numbers.

   1 x 3.125 = 3.125
   2 x 3.125 = 6.25
   3 x 3.125 = 9.375
   4 x 3.125 = 12.5
   5 x 3.125 = 15.625
   6 x 3.125 = 18.75
   7 x 3.125 = 21.875
   8 x 3.125 = 25

   Therefore the original number 25/8 = 3.125"

2. Some people realised that 0.125 is the same as $\frac{1}{8}$ and used this to help work out the answer.

   Well done to Daniel from Anglo-Chinese School, Singapore, Jesse from Tattingstone School, UK, Christina from Marlborough Primary School and Samantha .

   Thomas from Tattingstone School wrote:

   "One of the numbers is 8 and the other is 25. I worked this out by first looking at the number 0.125 and working out what fraction of 1 it is. It turned out that it was an eighth. That meant that one of the numbers must be 8. Then I looked at the remaining 3 and multiplied the 8 by it and that got me to 24. Last but definitely not least I added on the one and that got me to the last answer 25."

3. Ashley from Australia did it another way:

   "An easy way of working it out would be to say 'divide 3125 by 1000' (3.125). If I reduce it to its lowest terms, (divide by 125) is 25 divided by 8. This is the answer. It can't be 50 divided by 16, as the problem says that both numbers were under 50".

Thank you also to Robert , Stephanie , Ben , Sofie , Scot from Moorgate Primary School, Staffordshire. Ellie , Sarah and Caroline from The Mount School York.