动手学数学讨论与解答（41―45） 标签：速算与巧算

41

(Synergetics)

42

(RCBell)The Boardgame Book80

43

BA90°(90°)AACBBCACB90BC2AC

44

()为15.9cm×12.6cm×10.0cm

a×b×cabc

(a/2)

abcbca/2

acb2ab=2c2

b32c3

abc22/321/31

()21/311.261

45

(Boris Kordemsky)(The Moscow Puzzles)

图14

2×2E8(2)