Here we have a simple page which looks at adding three multiples of ten to make a variety of whole hundreds. It is quite open ended as there are many possible answers and the page could be repeated several times or used as the starting point for a mini investigation.
The page could be answerred very simply eg 280 + 10 + 10 = 300
but encourage children to make it as tricky as possible to show how good they are at maths;
e.g. 30 + 120 + 150.
This page can be found in our Year 3 Calculations category, together with many others.