don steward
maths teaching 10 ~ 16

Wednesday, 16 July 2014

enlargement scale factor root 2

a shape is shown
enlarge it by a scale factor that is the square root of 2
one of the shorter lengths or the shortest length is shown

then enlarge by this scale factor again
again a/the shorter/shortest length is shown
the shapes should not overlap with the original or each other

this can be done or confirmed by dissecting the shapes into simpler shapes (e.g. right angled triangles)
or you can use Pythagoras and multiply surds

students can compare the areas of the original and enlarged shapes

a previous version of this task seemed difficult:

Sunday, 13 July 2014

river crossing

some puzzles with a long history, variations appearing in many cultures

there are phone aps for several of these

a flash version of this at onlybestflash

 see wikipedia article

 NRICH 5916 goes full screen

Friday, 27 June 2014

Thursday, 26 June 2014

angle proofs

thanks to gogeometry
and the UKMT junior challenge
and Doug French, when he was at Hull University
for several of these ideas