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

Toán Lớp 5: a, tìm x : x nhân 2 +x nhân1/5 =1 và 3/5 b, tìm a: (6/7+1/4):(19/14-1/4)

Toán Lớp 5: a, tìm x : x nhân 2 +x nhân1/5 =1 và 3/5
b, tìm a: (6/7+1/4):(19/14-1/4)

Comments ( 2 )

  1. x * 2 + x * 1/5 = 1 3/5
    x * 2 + x * 1/5 = 8/5
    x * ( 2 + 1/5) = 8/5
    x * 11/5 = 8/5
    x            = 8/5 :  11/5
    x            = 8/11
    (6/7+1/4):(19/14-1/4)<a<7/3
    31/27 : 31/28 <a<7/3
    28/27<a<7/3
    28/27<a<63/27
    a = 29/27 —> 62/27
     

  2. a, x × 2 + x × $\dfrac{1}{5}$ = 1$\dfrac{3}{5}$
    x × 2 + x × $\dfrac{1}{5}$ = $\dfrac{8}{5}$
    x × (2 +$\dfrac{1}{5}$ )          = $\dfrac{8}{5}$ 
    x × $\dfrac{11}{5}$            = $\dfrac{8}{5}$
    x                     = $\dfrac{8}{5}$ : $\dfrac{11}{5}$
    x                      = $\dfrac{8}{11}$
    b, ($\dfrac{6}{7}$ + $\dfrac{1}{4}$): ( $\dfrac{19}{14}$-$\dfrac{1}{4}$)<a<$\dfrac{7}{3}$
    $\dfrac{31}{28}$ : $\dfrac{31}{28}$<a<$\dfrac{7}{3}$
    $\dfrac{31}{7}$<a<$\dfrac{3}{7}$
    ⇒ a = $\dfrac{30}{7}$, $\dfrac{29}{7}$, $\dfrac{28}{7}$,… $\dfrac{4}{7}$
    ~HT~
     

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