tính nhanh : a) 399 x 45 + 55 x399/ 1995 x 1996 – 1991 x 1995 b) 1996 x 1995 – 996/ 1000 + 1996 x 1994

0 bình luận về “tính nhanh : a) 399 x 45 + 55 x399/ 1995 x 1996 – 1991 x 1995 b) 1996 x 1995 – 996/ 1000 + 1996 x 1994”

1. a) `frac{399 × 45 + 55  × 399}{1995 × 1996 – 1991 × 1995}`

   = `frac{399 × (45 + 55)}{1995 × (1996 – 1991)}`

   = `frac{399 × 100}{1995 × 4}`

   = `frac{399 × 100}{399 × 5 × 4}`

   $= 4$

   b) `frac{1996 × 1995 – 996}{1000 + 1996 × 1994}`

   = `frac{1996 × (1994 + 1) – 996}{1000 + 1996 × 1994}`

   = `frac{1996 × 1994 + 1996 – 996}{1000 + 1996 × 1994}`

   =`frac{1996 × 1994 + 1000}{1000 + 1996 × 1994}`

   $= 1$

   c) `frac{637 x 527 – 189}{526 × 637 + 448}`

   = `frac{637 . (526 + 1) – 189}{526 . 637 + 448}`
   = `frac{637 . 526 + 637 – 189}{526 . 637 + 488}`
   = `frac{637 . 527 + 448}{526 . 637 + 488}`
   $= 1$
   

   d) `frac{677 × 874 + 251}{678 × 874 – 623}`

   = `frac{677 × 874 + 251}{(677 + 1) × 874 – 623}`
   

   = `frac{677 × 874 + 251}{677 × 874 + 874 – 623}`

   = `frac{677 × 874 + 251}{678 × 874 + 251}`

   $= 1$

    

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