What is the most reasonable metric measure for the width of a thumb tack?

10 mm is the most reasonable metric measure for the width of a thumb tack

And they say the education system hasn't been dumbed down.

The reasonable width is 10 mm which is equivalent to 1 cm

None of the above, write in '6 km'

WHy are people answering 40 mm? 40mm is over an inch and half, that's a pretty big thumbtack

The answer is 10mm (aka 1 cm).

You should get a meter stick with English units and just study it for a while.

1in = 2.54 cm

1 meter is a little bigger than a yard (3 feet)

1000mm = 1 m

how large do you think thumb tacks are!!!

10mm is equals to 1cm

40mm is 4cm

40cm is 40 cm

5kg is weight so dont even bother! now sit with a ruler and see these measurement and think hard about which one is best suited for this case!

40 mm.   I think you need to  get a hold of your measures.A kilogram is a weight of mass, and a thumbtack certainly doesn't weigh 2.2 lbs.

40 mm I think but dunno