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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 7: tính 3/1.4+3/4.7+3/7.10 +…+3/30.40 mình cần gấp

Toán Lớp 7: tính 3/1.4+3/4.7+3/7.10 +…+3/30.40 mình cần gấp

Comments ( 2 )

  1. ** Sai đề , sửa lại : 3/( 1 . 4 ) + 3/( 4 . 7 ) + 3/( 7 . 10 ) + …. + 3/( 37 . 40 )
    ** Bài làm :
    3/( 1 . 4 ) + 3/( 4 . 7 ) + 3/( 7 . 10 ) + …. + 3/( 37 . 40 )
    = 1/1 – 1/4 + 1/4 – 1/7 + 1/7 – 1/10 + …. + 1/37 – 1/40
    = 1 – 1/40
    = 39/40
     

  2. Giải đáp:
    \frac{3}{1.4} + \frac{3}{4.7} + \frac{3}{7.10} + … + \frac{3}{37.40}
    = 1 – \frac{1}{4} + \frac{1}{4} – \frac{1}{7} + \frac{1}{7} – \frac{1}{10} + … + \frac{1}{37} – \frac{1}{40}
    = 1 – \frac{1}{40}
    = \frac{39}{40}
    Chúc học tốt!!!
     
     

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222-9+11+12:2*14+14 = ? ( )