We have only looked at triangular numbers briefly during the Autumn term.  They should watch the Corbettmaths video first and then complete the worksheet.  They are representing the first ten triangular numbers as dot patterns.  The first three are already done as examples and they need to do the next seven in the same way.  The dots can be done in pencil or they could use colouring pencils or felt tips.  There is just enough room to fit them on the two sheets so it might be worth looking at the answers for a suggested way of setting them out.  They could list the numbers at the bottom of the page and even see if they can continue the list without drawing the patterns.  Email a photo if they extend the investigation.