reduction multiplication

some other questions:

• what is the largest number with an odd number root? 
• what is the common property of numbers that give an odd number root and why
• how nany numbers are there with an odd root?
• what happens to numbers with a 5 in them?
• by working backwards, find all of the 33 numbers that have a root of 5

this task is presented as 'Fossils' in 1000 problems (thanks to Puntmat for locating this for me - I had forgotten)