Hi there,

The real problem is that (many) teachers are no longer able to define a problem in such way that "one" only possible answer is correct.

Since no mention to the size and/or shape of the pieces (nor the original board) has been done, the problem has as many valid answers as one could imagine. Even the one propossed by the teacher!! and of course the one given by the alumn... and whatever Marie was able to saw... :-)

No need for the pieces to be of the same size or shape has been declared in the problem text... so: imagine a square board. Saw it into two identical rectangles. (10 min)

Saw one of these rectangles into two squares (5 min)

15 minutes in total, 3 pieces...

Saw the other rectangle into two more squares (5 min)

20 minutes in total, 4 pieces... sure you've got the idea...

Any amount of pieces can be achieved in any amout of time. In fact, the 10 minutes reference in the problem definition is basically useless since Marie could decide to start sawing a tiny corner... and then another one... or this corner into two pieces... or... whatever.

The more obvious is the one proposed by the alumn, three identical pieces from an original rectangle board require two cuts (20 min)

Agreed, this teacher should have the license revoked.

Cheers from the Caribbean Sea.

Diego.