TÝnh nhanh ph©n sè Bµi 1: TÝnh nhanh: 15151515 31313131 454545 989898 − = 101010115 101010131 1010145 1010198 x x x x − = 45 98 - 15 31 = 45 98 - 45 93 = 45 6 = 2/15 Bµi 2: TÝnh nhanh: 151515 424242 143143 165165 2121 1313 ) 951995199519 311931193119 19311931 19961996 1996 1995 ) ×× ×× b a VÝ dô 2: 199419961000 99619951996 ×+ −× ( ) 199419961000 )9961996(19941996 199419961000 996119941996 ×+ −+× = ×+ −+× = 199419961000 100019941996 ×+ +× = = 1(v× tö sè b»ng mÉu sè) a) Tính nhanh: 1997 1998 1 1998 1996 1997 × − × + = a) 199619971995 119961997 +× −× 253399254 145399254 ) ×+ −× b 100219971995 99519961997 ) +× −× c 6960015392 593160015392 ) −× ×+ d e) 199419951996 119971995 +× −× VÝ dô 3: 232323 242424 373737 535353 48 23 53 37 ××× 2 1 48 24 48 24 1 23 24 48 23 37 53 53 37 23 24 37 53 48 23 53 37 1010123 1010124 1010137 1010153 48 23 53 37 ==×=       ××       ×= ×××= × × × × × ××= Bµi 4: TÝnh nhanh: 2001 1001 2006 2004 2002 2008 2004 2001 2008 2006 ) 5 7 200019991998 120011999 ) ×××× × ×+ −× b a Bµi 5: TÝnh nhanh 1000 99 1000 87 . 1000 49 1000 37 1000 25 1000 13 1000 1 +++++++ Bµi 4: Cho: M = 39 37 . 15 13 11 9 7 5 3 1 ××××× N = 37 39 13 15 9 11 5 7 ×××× H·y tÝnh M × N. . TÝnh nhanh ph©n sè Bµi 1: TÝnh nhanh: 15151515 31313131 454545 989898 − = 101010115 101010131. × ××= Bµi 4: TÝnh nhanh: 2001 1001 2006 2004 2002 2008 2004 2001 2008 2006 ) 5 7 200019991998 120011999 ) ×××× × ×+ −× b a Bµi 5: TÝnh nhanh 1000 99 1000