A Maths Focus Group from Reigate Priory School wrote up the strategy they used to complete the jigsaw:
First we found the corners, which were pretty easy as they had to have $2$ black triangles.
Then we did the edges which have $1$ black triangle but we found that we had $4$ spare, $1$ from each edge.
We realised that these probably had to go together in the middle of the jigsaw, ie: with black triangles touching.
We then worked out the 'inner' corners, ie: the squares that had to have $2$ triangles matching, and then we worked out the squares that had to join these up.
After that there was only $1$ piece left to fit in the middle!!
Jamie from Great Sankey High School described his strategy:I looked at matching pairs first, and then tried to match them up into a group.